music21.meter

This module defines the TimeSignature object, as well as component objects for defining nested metrical structures, MeterTerminal and MeterSequence objects.

music21.meter.bestTimeSignature(meas)

Given a Measure with elements in it, get a TimeSignature that contains all elements.

Note: this does not yet accommodate triplets.

>>> from music21 import *
>>> s = converter.parse('C4 D4 E8 F8', format='tinyNotation')
>>> m = stream.Measure()
>>> for el in s:
...     m.insert(el.offset, el)
>>> ts = meter.bestTimeSignature(m)
>>> ts
<music21.meter.TimeSignature 3/4>

>>> s2 = converter.parse('C8. D16 E8 F8. G16 A8', format='tinyNotation')
>>> m2 = stream.Measure()
>>> for el in s2:
...     m2.insert(el.offset, el)
>>> ts2 = meter.bestTimeSignature(m2)
>>> ts2
<music21.meter.TimeSignature 6/8>
⁠
>>> s3 = converter.parse('C2 D2 E2', format='tinyNotation')
>>> m3 = stream.Measure()
>>> for el in s3:
...     m3.insert(el.offset, el)
>>> ts3 = meter.bestTimeSignature(m3)
>>> ts3
<music21.meter.TimeSignature 3/2>

>>> s4 = converter.parse('C8. D16 E8 F8. G16 A8 C4. D4.', format='tinyNotation')
>>> m4 = stream.Measure()
>>> for el in s4:
...     m4.insert(el.offset, el)
>>> ts4 = meter.bestTimeSignature(m4)
>>> ts4
<music21.meter.TimeSignature 12/8>
⁠
>>> s5 = converter.parse('C4 D2 E4 F2', format='tinyNotation')
>>> m5 = stream.Measure()
>>> for el in s5:
...     m5.insert(el.offset, el)
>>> ts5 = meter.bestTimeSignature(m5)
>>> ts5
<music21.meter.TimeSignature 6/4>

>>> s6 = converter.parse('C4 D16.', format='tinyNotation')
>>> m6 = stream.Measure()
>>> for el in s6:
...     m6.insert(el.offset, el)
>>> ts6 = meter.bestTimeSignature(m6)
>>> ts6
<music21.meter.TimeSignature 11/32>

music21.meter.fractionSum(fList)

Given a list of fractions represented as a list, find the sum

>>> from music21 import *
>>> meter.fractionSum([(3,8), (5,8), (1,8)])
(9, 8)
>>> meter.fractionSum([(1,6), (2,3)])
(5, 6)
>>> meter.fractionSum([(3,4), (1,2)])
(5, 4)
>>> meter.fractionSum([(1,13), (2,17)])
(43, 221)

music21.meter.fractionToSlashMixed(fList)

Given a list of fraction values, compact numerators by sum if denominators are the same

>>> from music21 import *
>>> meter.fractionToSlashMixed([(3, 8), (2, 8), (5, 8), (3, 4), (2, 16), (1, 16), (4, 16)])
[('3+2+5', 8), ('3', 4), ('2+1+4', 16)]

music21.meter.proportionToFraction(value)

Given a floating point proportional value between 0 and 1, return the best-fit slash-base fraction

>>> from music21 import *
>>> meter.proportionToFraction(.5)
(1, 2)
>>> meter.proportionToFraction(.25)
(1, 4)
>>> meter.proportionToFraction(.75)
(3, 4)
>>> meter.proportionToFraction(.125)
(1, 8)
>>> meter.proportionToFraction(.375)
(3, 8)
>>> meter.proportionToFraction(.625)
(5, 8)
>>> meter.proportionToFraction(.333)
(1, 3)
>>> meter.proportionToFraction(0.83333)
(5, 6)

music21.meter.slashCompoundToFraction(value)

>>> from music21 import *
>>> meter.slashCompoundToFraction('3/8+2/8')
[(3, 8), (2, 8)]
>>> meter.slashCompoundToFraction('5/8')
[(5, 8)]
>>> meter.slashCompoundToFraction('5/8+2/4+6/8')
[(5, 8), (2, 4), (6, 8)]

music21.meter.slashMixedToFraction(valueSrc)

Given a mixture if possible meter fraction representations, return a list of pairs. If originally given as a summed numerator; break into separate fractions.

>>> from music21 import *
>>> meter.slashMixedToFraction('3/8+2/8')
([(3, 8), (2, 8)], False)
⁠
>>> meter.slashMixedToFraction('3+2/8')
([(3, 8), (2, 8)], True)

>>> meter.slashMixedToFraction('3+2+5/8')
([(3, 8), (2, 8), (5, 8)], True)
⁠
>>> meter.slashMixedToFraction('3+2+5/8+3/4')
([(3, 8), (2, 8), (5, 8), (3, 4)], True)

>>> meter.slashMixedToFraction('3+2+5/8+3/4+2+1+4/16')
([(3, 8), (2, 8), (5, 8), (3, 4), (2, 16), (1, 16), (4, 16)], True)
⁠
>>> meter.slashMixedToFraction('3+2+5/8+3/4+2+1+4')
Traceback (most recent call last):
...
MeterException: cannot match denominator to numerator in: 3+2+5/8+3/4+2+1+4

music21.meter.slashToFraction(value)

>>> from music21 import *
>>> meter.slashToFraction('3/8')
(3, 8, None)
>>> meter.slashToFraction('7/32')
(7, 32, None)
>>> meter.slashToFraction('slow 6/8')
(6, 8, 'slow')

TimeSignature

Inherits from: Music21Object

class music21.meter.TimeSignature(value='4/4', partitionRequest=None)

The TimeSignature object representes time signatures in musical scores (4/4, 3/8, 2/4+5/16, Cut, etc.).

TimeSignatures should be present in the first Measure of each Part that they apply to. Alternatively you can put the time signature at the front of a Part or at the beginning of a Score and they will work within music21 but they won’t necessarily display properly in musicxml, lilypond, etc. So best is to create structures like this:

>>> from music21 import *
>>> s = stream.Score()
>>> p = stream.Part()
>>> m1 = stream.Measure()
>>> ts = meter.TimeSignature('3/4')
>>> m1.insert(0, ts)
>>> m1.insert(0, note.HalfNote("C#3"))
>>> n = note.QuarterNote("D3") # we will need this later
>>> m1.insert(1.0, n)
>>> m1.number = 1
>>> p.insert(0, m1)
>>> s.insert(0, p)
>>> s.show('t')
{0.0} <music21.stream.Part ...>
    {0.0} <music21.stream.Measure 1 offset=0.0>
        {0.0} <music21.meter.TimeSignature 3/4>
        {0.0} <music21.note.Note C#>
        {1.0} <music21.note.Note D>

Basic operations on a TimeSignature object are designed to be very simple.

>>> ts.ratioString
'3/4'
>>> ts.numerator
3
>>> ts.beatCount
3
>>> ts.beatCountName
'Triple'
>>> ts.beatDuration.quarterLength
1.0

As an alternative to putting a TimeSignature in a Stream at a specific position (offset), it can be assigned to a special property in Measure that positions the TimeSignature at the start of a Measure. Notice that when we show() the Measure (or if we iterate through it), the TimeSignature appears as if it’s in the measure itself:

>>> m2 = stream.Measure()
>>> m2.number = 2
>>> ts2 = meter.TimeSignature('2/4')
>>> m2.timeSignature = ts2
>>> m2.append(note.HalfNote("E3"))
>>> p.append(m2)
>>> s.show('text')
{0.0} <music21.stream.Part ...>
    {0.0} <music21.stream.Measure 1 offset=0.0>
        {0.0} <music21.meter.TimeSignature 3/4>
        {0.0} <music21.note.Note C#>
        {1.0} <music21.note.Note D>
    {2.0} <music21.stream.Measure 2 offset=2.0>
        {0.0} <music21.meter.TimeSignature 2/4>
        {0.0} <music21.note.Note E>

Once a Note has a local TimeSignature, a Note can get its beat position and other meter-specific parameters. Remember n, our quarter note at offset 2.0 of m1, a 3/4 measure? Let’s get its beat:

>>> n.beat
2.0

This feature is more useful if there are more beats:

>>> m3 = stream.Measure()
>>> m3.timeSignature = meter.TimeSignature('3/4')
>>> eighth = note.EighthNote()
>>> m3.repeatAppend(eighth, 6)
>>> [thisNote.beatStr for thisNote in m3.notes]
['1', '1 1/2', '2', '2 1/2', '3', '3 1/2']

Now lets change its measure’s TimeSignature and see what happens:

>>> sixEight = meter.TimeSignature('6/8')
>>> m3.timeSignature = sixEight
>>> [thisNote.beatStr for thisNote in m3.notes]
['1', '1 1/3', '1 2/3', '2', '2 1/3', '2 2/3']

TimeSignature(‘6/8’) defaults to fast 6/8:

>>> sixEight.beatCount
2
>>> sixEight.beatDuration.quarterLength
1.5
>>> sixEight.beatDivisionCountName
'Compound'

Let’s make it slow 6/8 instead:

>>> sixEight.beatCount = 6
>>> sixEight.beatDuration.quarterLength
0.5
>>> sixEight.beatDivisionCountName
'Simple'

Now let’s look at the beatStr for each of the notes in m3:

>>> [thisNote.beatStr for thisNote in m3.notes]
['1', '2', '3', '4', '5', '6']

TimeSignatures can also use symbols instead of numbers

>>> tsCommon = meter.TimeSignature('c')  # or common
>>> tsCommon.beatCount
4
>>> tsCommon.denominator
4
>>> tsCommon.symbol
'common'

>>> tsCut = meter.TimeSignature("cut")
>>> tsCut.beatCount
2
>>> tsCut.denominator
2
>>> tsCut.symbol
'cut'

For complete details on using this object, see Overview: Meters, Time Signatures, and Processing Beams, Accents, and Beats.

That’s it for the simple aspects of TimeSignature objects. You know enough to get started now!

Under the hood, they’re extremely powerful. For musicians, TimeSignatures do (at least) three different things:

• They define where the beats in the measure are and how many there are.
• They indicate how the notes should be beamed
• They give a sense of how much accent or weight each note gets, which also defines which are important notes and which might be ornaments.

These three aspects of TimeSignatures are controlled by the beatSequence, beamSequence, and accentSequence properties of the TimeSignature. Each of them is an independent MeterSequence element which might have nested properties (e.g., a 11/16 meter might be beamed as {1/4+1/4+{1/8+1/16}} ), so if you want to change how beats are calculated or beams are generated you’ll want to learn more about meter.MeterSequence objects.

There’s a fourth MeterSequence object inside a TimeSignature, and that is the displaySequence. That determines how the TimeSignature should actually look on paper. Normally this MeterSequence is pretty simple. In ‘4/4’ it’s usually just ‘4/4’. But if you have the ‘11/16’ time above, you may want to have it displayed as ‘2/4+3/16’ or ‘11/16 (2/4+3/16)’. Or you might want the written TimeSignature to contradict what the notes imply. All this can be done with .displaySequence.

TimeSignature attributes

beamSequence

A MeterSequence governing automatic beaming.

symbolizeDenominator

If set to True (default is False) then the denominator will be displayed as a symbol rather than a number. Hindemith uses this in his scores. Finale and other MusicXML readers do not support this so don’t expect proper output yet.

symbol

A string representation of how to display the TimeSignature. can be “common”, “cut”, “single-number” (i.e., no denominator), or “normal” or “”.

beatSequence

A MeterSequence governing beat partitioning.

displaySequence

A MeterSequence governing the display of the TimeSignature.

accentSequence

A MeterSequence governing accent partitioning.

Attributes without Documentation: classSortOrder, summedNumerator

Attributes inherited from Music21Object: isSpanner, isStream, isVariant, xPosition, id, sites, groups, hideObjectOnPrint

TimeSignature properties

barDuration

Return a Duration object equal to the total length of this TimeSignature.

>>> from music21 import *
>>> ts = meter.TimeSignature('5/16')
>>> ts.barDuration
<music21.duration.Duration 1.25>

beatCount

Return or set the count of beat units, or the number of beats in this TimeSignature.

When setting beat units, one level of sub-partitions is automatically defined. Users can provide beat count values as integers or as lists of durations. For more precise configuration of the beat MeterSequence, manipulate the .beatSequence attribute directly.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.beatCount
3
>>> ts.beatDuration.quarterLength
1.0
>>> ts.beatCount = [1,1,1,1,1,1]
>>> ts.beatCount
6
>>> ts.beatDuration.quarterLength
0.5

beatCountName

Return the beat count name, or the name given for the number of beat units. For example, 2/4 is duple; 9/4 is triple.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.beatCountName
'Triple'
⁠
>>> ts = meter.TimeSignature('6/8')
>>> ts.beatCountName
'Duple'

beatDivisionCount

Return the count of background beat units found within one beat, or the number of subdivisions in the beat unit in this TimeSignature.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDivisionCount
2
⁠
>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDivisionCount
3

>>> ts = meter.TimeSignature('15/8')
>>> ts.beatDivisionCount
3
⁠
>>> ts = meter.TimeSignature('3/8')
>>> ts.beatDivisionCount
2

>>> ts = meter.TimeSignature('13/8', 13)
>>> ts.beatDivisionCount
Traceback (most recent call last):
TimeSignatureException: cannot determine beat backgrond when each beat is not partitioned

beatDivisionCountName

Return the beat count name, or the name given for the number of beat units. For example, 2/4 is duple; 9/4 is triple.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDivisionCountName
'Simple'
⁠
>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDivisionCountName
'Compound'

beatDivisionDurations

Return the beat division, or the durations that make up one beat, as a list of Duration objects, if and only if the TimeSignature has a uniform beat division for all beats.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDivisionDurations
[<music21.duration.Duration 0.5>, <music21.duration.Duration 0.5>]
⁠
>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDivisionDurations
[<music21.duration.Duration 0.5>, <music21.duration.Duration 0.5>, <music21.duration.Duration 0.5>]

beatDuration

Return a Duration object equal to the beat unit of this Time Signature, if and only if this TimeSignatyure has a uniform beat unit.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDuration
<music21.duration.Duration 1.0>
>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDuration
<music21.duration.Duration 1.5>
⁠
>>> ts = meter.TimeSignature('7/8')
>>> ts.beatDuration
<music21.duration.Duration 0.5>

beatLengthToQuarterLengthRatio

>>> from music21 import *
>>> a = meter.TimeSignature('3/2')
>>> a.beatLengthToQuarterLengthRatio
2.0

beatSubDivisionDurations

Return a subdivision of the beat division, or a list of Duration objects representing each beat division divided by two.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.beatSubDivisionDurations
[<music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>]
⁠
>>> ts = meter.TimeSignature('6/8')
>>> ts.beatSubDivisionDurations
[<music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>]

classification

Return the classification of this TimeSignature, such as Simple Triple or Compound Quadruple.

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.classification
'Simple Triple'
>>> ts = meter.TimeSignature('6/8')
>>> ts.classification
'Compound Duple'
>>> ts = meter.TimeSignature('4/32')
>>> ts.classification
'Simple Quadruple'

denominator

Return the denominator of the TimeSignature as a number

(for complex TimeSignatures, note that this comes from the .beamSequence of the TimeSignature)

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.denominator
4

In this case, the TimeSignature is silently being converted to 9/8 to get a single digit denominator:

>>> ts = meter.TimeSignature('2/4+5/8')
>>> ts.denominator
8

numerator

Return the numerator of the TimeSignature as a number. To set the numerator, change beatCount.

(for complex TimeSignatures, note that this comes from the .beamSequence of the TimeSignature)

>>> from music21 import *
>>> ts = meter.TimeSignature('3/4')
>>> ts.numerator
3

In this case, the TimeSignature is silently being converted to 9/8 to get a single digit numerator:

>>> ts = meter.TimeSignature('2/4+5/8')
>>> ts.numerator
9

quarterLengthToBeatLengthRatio

No documentation.

ratioString

returns a simple string representing the time signature ratio or sets a new one. Cannot be used for very complex time signatures:

>>> from music21 import *
>>> threeFour = meter.TimeSignature('3/4')
>>> threeFour.ratioString
'3/4'
⁠
>>> threeFour.ratioString = '5/8'
>>> threeFour.numerator
5
>>> threeFour.denominator
8

totalLength

Total length of the TimeSignature, in Quarter Lengths.

>>> from music21 import *
>>> ts = meter.TimeSignature('6/8')
>>> ts.totalLength
3.0

Properties inherited from Music21Object: classes, fullyQualifiedClasses, activeSite, beat, beatStr, beatStrength, derivationHierarchy, duration, isGrace, measureNumber, offset, priority, seconds

TimeSignature methods

averageBeatStrength(streamIn, notesOnly=True)

returns a float of the average beat strength of all objects (or if notesOnly is True [default] only the notes) in the Stream specified as streamIn.

>>> from music21 import *
>>> s = converter.parse('C4 D4 E8 F8', format='tinyNotation')
>>> sixEight = meter.TimeSignature('6/8')
>>> sixEight.averageBeatStrength(s)
0.4375
>>> threeFour = meter.TimeSignature('3/4')
>>> threeFour.averageBeatStrength(s)
0.5625

If notesOnly is False then test objects will give added weight to the beginning of the measure:

>>> sixEight.averageBeatStrength(s, notesOnly=False)
0.4375
>>> s.insert(0.0, clef.TrebleClef())
>>> s.insert(0.0, clef.BassClef())
>>> sixEight.averageBeatStrength(s, notesOnly=False)
0.625

getAccent(qLenPos)

Return True or False if the qLenPos is at the start of an accent division.

>>> from music21 import *
>>> a = meter.TimeSignature('3/4', 3)
>>> a.accentSequence.partition([2,1])
>>> a.accentSequence
<MeterSequence {2/4+1/4}>
>>> a.getAccent(0)
True
>>> a.getAccent(1)
False
>>> a.getAccent(2)
True

getAccentWeight(qLenPos, level=0, forcePositionMatch=False, permitMeterModulus=False)

Given a qLenPos, return an accent level. In general, accents are assumed to define only a first-level weight.

If forcePositionMatch is True, an accent will only be returned if the provided qLenPos is a near exact match to the provided quarter length. Otherwise, half of the minimum quarter length will be provided.

If permitMeterModulus is True, quarter length positions greater than the duration of the Meter will be accepted as the modulus of the total meter duration.

>>> from music21 import *
>>> ts1 = meter.TimeSignature('3/4')
>>> [ts1.getAccentWeight(x) for x in range(3)]
[1.0, 0.5, 0.5]

getBeams(srcList, measureStartOffset=0.0)

Given a qLen position and a list of Duration objects, return a list of Beams object.

Can alternatively provide a flat stream, from which Durations are extracted.

Duration objects are assumed to be adjoining; offsets are not used.

This can be modified to take lists of rests and notes

Must process a list at time, because we cannot tell when a beam ends unless we see the context of adjoining durations.

>>> from music21 import *
>>> a = meter.TimeSignature('2/4', 2)
>>> a.beamSequence[0] = a.beamSequence[0].subdivide(2)
>>> a.beamSequence[1] = a.beamSequence[1].subdivide(2)
>>> a.beamSequence
<MeterSequence {{1/8+1/8}+{1/8+1/8}}>
>>> b = [duration.Duration('16th')] * 8
>>> c = a.getBeams(b)
>>> len(c) == len(b)
True
>>> print(c)
[<music21.beam.Beams <music21.beam.Beam 1/start>/<music21.beam.Beam 2/start>>, <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/stop>>, <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/start>>, <music21.beam.Beams <music21.beam.Beam 1/stop>/<music21.beam.Beam 2/stop>>, <music21.beam.Beams <music21.beam.Beam 1/start>/<music21.beam.Beam 2/start>>, <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/stop>>, <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/start>>, <music21.beam.Beams <music21.beam.Beam 1/stop>/<music21.beam.Beam 2/stop>>]
⁠
>>> a = meter.TimeSignature('6/8')
>>> b = [duration.Duration('eighth')] * 6
>>> c = a.getBeams(b)
>>> print(c)
[<music21.beam.Beams <music21.beam.Beam 1/start>>, <music21.beam.Beams <music21.beam.Beam 1/continue>>, <music21.beam.Beams <music21.beam.Beam 1/stop>>, <music21.beam.Beams <music21.beam.Beam 1/start>>, <music21.beam.Beams <music21.beam.Beam 1/continue>>, <music21.beam.Beams <music21.beam.Beam 1/stop>>]

>>> fourFour = meter.TimeSignature('4/4')
>>> d = duration.Duration
>>> dList = [d('eighth'), d('quarter'), d('eighth'), d('eighth'), d('quarter'), d('eighth')]
>>> beamList = fourFour.getBeams(dList)
>>> print(beamList)
[None, None, None, None, None, None]

Pickup measure support included by taking in an additional measureStartOffset argument.

>>> threeFour = meter.TimeSignature("3/4")
>>> dList = [d('eighth'), d('eighth'), d('eighth')]
>>> beamList = threeFour.getBeams(dList, measureStartOffset=1.5)
>>> print(beamList)
[<music21.beam.Beams <music21.beam.Beam 1/start>>, <music21.beam.Beams <music21.beam.Beam 1/continue>>, <music21.beam.Beams <music21.beam.Beam 1/stop>>]

getBeat(offset)

Given an offset (quarterLength position), get the beat, where beats count from 1

If you want a floating point number for the beat, see getBeatProportion.

In v.1.4 – getBeat will probably do what getBeatProportion does now...

>>> from music21 import *
>>> a = meter.TimeSignature('3/4', 3)
>>> a.getBeat(0)
1
>>> a.getBeat(2.5)
3
>>> a.beatSequence.partition(['3/8', '3/8'])
>>> a.getBeat(2.5)
2

getBeatDepth(qLenPos, align='quantize')

Return the number of levels of beat partitioning given a QL into the TimeSignature. Note that by default beat partitioning always has a single, top-level partition.

The align parameter is passed to the offsetToDepth() method, and can be used to find depths based on start position overlaps.

>>> from music21 import *
>>> a = TimeSignature('3/4', 3)
>>> a.getBeatDepth(0)
1
>>> a.getBeatDepth(1)
1
>>> a.getBeatDepth(2)
1
⁠
>>> b = TimeSignature('3/4', 1)
>>> b.beatSequence[0] = b.beatSequence[0].subdivide(3)
>>> b.beatSequence[0][0] = b.beatSequence[0][0].subdivide(2)
>>> b.beatSequence[0][1] = b.beatSequence[0][1].subdivide(2)
>>> b.beatSequence[0][2] = b.beatSequence[0][2].subdivide(2)
>>> b.getBeatDepth(0)
3
>>> b.getBeatDepth(.5)
1
>>> b.getBeatDepth(1)
2

getBeatDuration(qLenPos)

Returns a Duration object representing the length of the beat found at qLenPos. For most standard meters, you can give qLenPos = 0 and get the length of any beat in the TimeSignature; but the simpler music21.meter.TimeSignature.beatDuration parameter, will do that for you just as well.

The advantage of this method is that it will work for asymmetrical meters, as the second example shows.

Ex. 1: beat duration for 3/4 is always 1.0 no matter where in the meter you query.

>>> from music21 import *
>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getBeatDuration(.5)
<music21.duration.Duration 1.0>
>>> ts1.getBeatDuration(2.5)
<music21.duration.Duration 1.0>

Ex. 2: same for 6/8:

>>> ts2 = meter.TimeSignature('6/8')
>>> ts2.getBeatDuration(2.5)
<music21.duration.Duration 1.5>

Ex. 3: but for a compound meter of 3/8 + 2/8, where you ask for the beat duration will determine the length of the beat:

>>> ts3 = meter.TimeSignature(['3/8','2/8']) # will partition as 2 beat
>>> ts3.getBeatDuration(.5)
<music21.duration.Duration 1.5>
>>> ts3.getBeatDuration(1.5)
<music21.duration.Duration 1.0>

getBeatOffsets()

Return offset positions in a list for the start of each beat, assuming this object is found at offset zero.

>>> from music21 import *
>>> a = meter.TimeSignature('3/4')
>>> a.getBeatOffsets()
[0.0, 1.0, 2.0]
>>> a = meter.TimeSignature('6/8')
>>> a.getBeatOffsets()
[0.0, 1.5]

getBeatProgress(qLenPos)

Given a quarterLength position, get the beat, where beats count from 1, and return the the amount of qLen into this beat the supplied qLenPos is.

>>> from music21 import *
>>> a = meter.TimeSignature('3/4', 3)
>>> a.getBeatProgress(0)
(1, 0)
>>> a.getBeatProgress(0.75)
(1, 0.75)
>>> a.getBeatProgress(1.0)
(2, 0.0)
>>> a.getBeatProgress(2.5)
(3, 0.5)

Works for specifically partitioned meters too:

>>> a.beatSequence.partition(['3/8', '3/8'])
>>> a.getBeatProgress(2.5)
(2, 1.0)

getBeatProportion(qLenPos)

Given a quarter length position into the meter, return a numerical progress through the beat (where beats count from one) with a floating-point value between 0 and 1 appended to this value that gives the proportional progress into the beat.

For faster, integer values, use simply .getBeat()

>>> from music21 import *
>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getBeatProportion(0.0)
1.0
>>> ts1.getBeatProportion(0.5)
1.5
>>> ts1.getBeatProportion(1.0)
2.0
⁠
>>> ts3 = meter.TimeSignature(['3/8','2/8']) # will partition as 2 beat
>>> ts3.getBeatProportion(.75)
1.5
>>> ts3.getBeatProportion(2.0)
2.5

getBeatProportionStr(qLenPos)

Return a string presentation of the beat.

>>> from music21 import *
>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getBeatProportionStr(0.0)
'1'
>>> ts1.getBeatProportionStr(0.5)
'1 1/2'
>>> ts1.getBeatProportionStr(1.0)
'2'
>>> ts3 = meter.TimeSignature(['3/8','2/8']) # will partition as 2 beat
>>> ts3.getBeatProportionStr(.75)
'1 1/2'
>>> ts3.getBeatProportionStr(2)
'2 1/2'
⁠
>>> ts4 = meter.TimeSignature(['6/8']) # will partition as 2 beat

getOffsetFromBeat(beat)

Given a beat value, convert into an offset position.

>>> from music21 import *
>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getOffsetFromBeat(1)
0.0
>>> ts1.getOffsetFromBeat(2)
1.0
>>> ts1.getOffsetFromBeat(3)
2.0
>>> ts1.getOffsetFromBeat(3.5)
2.5
>>> ts1.getOffsetFromBeat(3.25)
2.25
⁠
>>> ts1 = meter.TimeSignature('6/8')
>>> ts1.getOffsetFromBeat(1)
0.0
>>> ts1.getOffsetFromBeat(2)
1.5
>>> ts1.getOffsetFromBeat(2.33)
2.0
>>> ts1.getOffsetFromBeat(2.5) # will be + .5 * 1.5
2.25
>>> ts1.getOffsetFromBeat(2.66)
2.5

Works for asymmetrical meters as well:

>>> ts3 = meter.TimeSignature(['3/8','2/8']) # will partition as 2 beat
>>> ts3.getOffsetFromBeat(1)
0.0
>>> ts3.getOffsetFromBeat(2)
1.5
>>> ts3.getOffsetFromBeat(1.66)
1.0
>>> ts3.getOffsetFromBeat(2.5)
2.0

Let’s try this on a real piece, a 4/4 chorale with a one beat pickup. Here we get the normal offset from the active TimeSignature but we subtract out the pickup length which is in a Measure‘s paddingLeft property.

>>> c = corpus.parse('bwv1.6')
>>> for m in c.parts[0].getElementsByClass('Measure'):
...     print m.number, m.getContextByClass('TimeSignature').getOffsetFromBeat(4.5) - m.paddingLeft
0 0.5
1 3.5
2 3.5
...

load(value, partitionRequest=None)

Loading a meter destroys all internal representations

loadRatio(numerator, denominator, partitionRequest=None)

Convenience method

quarteroffsetToBeat(currentQtrPosition=0)

For backward compatibility. Ultimately, remove.

ratioEqual(other)

A basic form of comparison; does not determine if any internatl structures are equal; only outermost ratio.

resetValues(value='4/4', partitionRequest=None)

reset all values according to a new value and partitionRequest

setAccentWeight(weightList, level=0)

Set accent weight, or floating point scalars, for the accent MeterSequence. Provide a list of values; if this list is shorter than the length of the MeterSequence, it will be looped; if this list is longer, only the first relevant value will be used.

If the accent MeterSequence is subdivided, the level of depth to set is given by the optional level argument.

>>> from music21 import *
>>> a = meter.TimeSignature('4/4', 4)
>>> len(a.accentSequence)
4
>>> a.setAccentWeight([.8, .2])
>>> a.getAccentWeight(0)
0.8...
>>> a.getAccentWeight(.5)
0.8...
>>> a.getAccentWeight(1)
0.2...
>>> a.getAccentWeight(2.5)
0.8...
>>> a.getAccentWeight(3.5)
0.2...

setDisplay(value, partitionRequest=None)

Set an independent display value for a meter.

>>> from music21 import *
>>> a = meter.TimeSignature()
>>> a.load('3/4')
>>> a.setDisplay('2/8+2/8+2/8')
>>> a.displaySequence
<MeterSequence {2/8+2/8+2/8}>
>>> a.beamSequence
<MeterSequence {{1/8+1/8}+{1/8+1/8}+{1/8+1/8}}>
>>> a.beatSequence # a single top-level partition is default for beat
<MeterSequence {{1/8+1/8}+{1/8+1/8}+{1/8+1/8}}>
>>> a.setDisplay('3/4')
>>> a.displaySequence
<MeterSequence {3/4}>

Methods inherited from Music21Object: findAttributeInHierarchy(), getContextAttr(), setContextAttr(), addContext(), addLocation(), getAllContextsByClass(), getContextByClass(), getOffsetBySite(), getSiteIds(), getSites(), getSpannerSites(), hasContext(), hasSite(), hasSpannerSite(), hasVariantSite(), isClassOrSubclass(), mergeAttributes(), next(), previous(), purgeLocations(), purgeOrphans(), removeLocationBySite(), removeLocationBySiteId(), setOffsetBySite(), show(), splitAtDurations(), splitAtQuarterLength(), splitByQuarterLengths(), unwrapWeakref(), wrapWeakref(), write()

CompoundTimeSignature

Inherits from: TimeSignature, Music21Object

class music21.meter.CompoundTimeSignature(value='4/4', partitionRequest=None)

DurationDenominatorTimeSignature

Inherits from: TimeSignature, Music21Object

class music21.meter.DurationDenominatorTimeSignature(value='4/4', partitionRequest=None)

If you have played Hindemith you know these, 3/(dot-quarter) etc.

MeterSequence

Inherits from: MeterTerminal

class music21.meter.MeterSequence(value=None, partitionRequest=None)

A meter sequence is a list of MeterTerminals, or other MeterSequences

MeterSequence attributes

Attributes without Documentation: parenthesis, summedNumerator

MeterSequence properties

denominator

No documentation.

depth

Return how many unique levels deep this part is This should be optimized to store values unless the structure has changed.

flat

Return a new MeterSequence composed of the flattend representation.

>>> from music21 import *
>>> a = meter.MeterSequence('3/4', 3)
>>> b = a.flat
>>> len(b)
3
⁠
>>> a[1] = a[1].subdivide(4)
>>> b = a.flat
>>> len(b)
6

>>> a[1][2] = a[1][2].subdivide(4)
>>> a
<MeterSequence {1/4+{1/16+1/16+{1/64+1/64+1/64+1/64}+1/16}+1/4}>
>>> b = a.flat
>>> len(b)
9

flatWeight

Return a list of flat weight valuess

numerator

No documentation.

partitionStr

Return the number of top-level partitions in this MeterSequence as a string.

>>> from music21 import *
>>> ms = meter.MeterSequence('2/4+2/4')
>>> ms
<MeterSequence {2/4+2/4}>
>>> ms.partitionStr
'Duple'
⁠
>>> ms = meter.MeterSequence('6/4', 6)
>>> ms
<MeterSequence {1/4+1/4+1/4+1/4+1/4+1/4}>
>>> ms.partitionStr
'Sextuple'

>>> ms = meter.MeterSequence('6/4', 2)
>>> ms.partitionStr
'Duple'
⁠
>>> ms = meter.MeterSequence('6/4', 3)
>>> ms.partitionStr
'Triple'

weight

>>> from music21 import *
>>> a = meter.MeterSequence('3/4')
>>> a.partition(3)
>>> a.weight = 1
>>> a[0].weight
0.333...
>>> b = meter.MeterTerminal('1/4', .25)
>>> c = meter.MeterTerminal('1/4', .25)
>>> d = meter.MeterSequence([b, c])
>>> d.weight
0.5

Properties inherited from MeterTerminal: duration

MeterSequence methods

getLevel(level=0, flat=True)

Return a complete MeterSequence with the same numerator/denominator reationship but that represents any partitions found at the rquested level. A sort of flatness with variable depth.

>>> from music21 import *
>>> b = meter.MeterSequence('4/4', 4)
>>> b[1] = b[1].subdivide(2)
>>> b[3] = b[3].subdivide(2)
>>> b[3][0] = b[3][0].subdivide(2)
>>> b
<MeterSequence {1/4+{1/8+1/8}+1/4+{{1/16+1/16}+1/8}}>
>>> b.getLevel(0)
<MeterSequence {1/4+1/4+1/4+1/4}>
>>> b.getLevel(1)
<MeterSequence {1/4+1/8+1/8+1/4+1/8+1/8}>
>>> b.getLevel(2)
<MeterSequence {1/4+1/8+1/8+1/4+1/16+1/16+1/8}>

getLevelSpan(level=0)

For a given level, return the time span of each terminal or sequnece

>>> from music21 import *
>>> b = meter.MeterSequence('4/4', 4)
>>> b[1] = b[1].subdivide(2)
>>> b[3] = b[3].subdivide(2)
>>> b[3][0] = b[3][0].subdivide(2)
>>> b
<MeterSequence {1/4+{1/8+1/8}+1/4+{{1/16+1/16}+1/8}}>
>>> b.getLevelSpan(0)
[(0.0, 1.0), (1.0, 2.0), (2.0, 3.0), (3.0, 4.0)]
>>> b.getLevelSpan(1)
[(0.0, 1.0), (1.0, 1.5), (1.5, 2.0), (2.0, 3.0), (3.0, 3.5), (3.5, 4.0)]
>>> b.getLevelSpan(2)
[(0.0, 1.0), (1.0, 1.5), (1.5, 2.0), (2.0, 3.0), (3.0, 3.25), (3.25, 3.5), (3.5, 4.0)]

getLevelWeight(level=0)

The weightList is an array of weights found in the components. The MeterSequence has a ._weight attribute, but it is not used here

>>> from music21 import *
>>> a = meter.MeterSequence('4/4', 4)
>>> a.getLevelWeight()
[0.25, 0.25, 0.25, 0.25]
⁠
>>> b = meter.MeterSequence('4/4', 4)
>>> b.getLevelWeight(0)
[0.25, 0.25, 0.25, 0.25]

>>> b[1] = b[1].subdivide(2)
>>> b[3] = b[3].subdivide(2)
>>> b.getLevelWeight(0)
[0.25, 0.25, 0.25, 0.25]
⁠
>>> b[3][0] = b[3][0].subdivide(2)
>>> b
<MeterSequence {1/4+{1/8+1/8}+1/4+{{1/16+1/16}+1/8}}>
>>> b.getLevelWeight(0)
[0.25, 0.25, 0.25, 0.25]
>>> b.getLevelWeight(1)
[0.25, 0.125, 0.125, 0.25, 0.125, 0.125]
>>> b.getLevelWeight(2)
[0.25, 0.125, 0.125, 0.25, 0.0625, 0.0625, 0.125]

isUniformPartition(depth=0)

Return True if the top-level partitions have equal durations

>>> from music21 import *
>>> ms = meter.MeterSequence('3/8+2/8+3/4')
>>> ms.isUniformPartition()
False
>>> ms = meter.MeterSequence('4/4')
>>> ms.isUniformPartition()
True
>>> ms = meter.MeterSequence('2/4+2/4')
>>> ms.isUniformPartition()
True
⁠
>>> ms = meter.MeterSequence('5/8', 5)
>>> ms.isUniformPartition()
True
>>> ms.partition(2)
>>> ms.isUniformPartition()
False

load(value, partitionRequest=None, autoWeight=False, targetWeight=None)

This method is called when a MeterSequence is created, or if a MeterSequence is re-set.

User can enter a list of values or an abbreviated slash notation.

autoWeight, if True, will attempt to set weights. tragetWeight, if given, will be used instead of self.weight

loading is a destructive operation.

>>> from music21 import *
>>> a = meter.MeterSequence()
>>> a.load('4/4', 4)
>>> str(a)
'{1/4+1/4+1/4+1/4}'
⁠
>>> a.load('4/4', 2) # request 2 beats
>>> str(a)
'{1/2+1/2}'

>>> a.load('5/8', 2) # request 2 beats
>>> str(a)
'{2/8+3/8}'
⁠
>>> a.load('5/8+4/4')
>>> str(a)
'{5/8+4/4}'

offsetToAddress(qLenPos, includeCoincidentBoundaries=False)

Give a list of values that show all indices necessary to access the exact terminal at a given qLenPos.

The len of the returned list also provides the depth at the specified qLen.

>>> from music21 import *
>>> a = meter.MeterSequence('3/4', 3)
>>> a[1] = a[1].subdivide(4)
>>> a
<MeterSequence {1/4+{1/16+1/16+1/16+1/16}+1/4}>
>>> len(a)
3
>>> a.offsetToAddress(.5)
[0]
>>> a[0]
<MeterTerminal 1/4>
>>> a.offsetToAddress(1.0)
[1, 0]
>>> a.offsetToAddress(1.5)
[1, 2]
>>> a[1][2]
<MeterTerminal 1/16>
>>> a.offsetToAddress(1.99)
[1, 3]
>>> a.offsetToAddress(2.5)
[2]

offsetToDepth(qLenPos, align='quantize')

Given a qLenPos, return the maximum available depth at this position

>>> from music21 import *
>>> b = meter.MeterSequence('4/4', 4)
>>> b[1] = b[1].subdivide(2)
>>> b[3] = b[3].subdivide(2)
>>> b[3][0] = b[3][0].subdivide(2)
>>> b
<MeterSequence {1/4+{1/8+1/8}+1/4+{{1/16+1/16}+1/8}}>
>>> b.offsetToDepth(0)
3
>>> b.offsetToDepth(0.25) # quantizing active by default
3
>>> b.offsetToDepth(1)
3
>>> b.offsetToDepth(1.5)
2

offsetToIndex(qLenPos, includeCoincidentBoundaries=False)

Given an offset in quarterLengths (0.0 through self.duration.quarterLength), return the index of the active MeterTerminal or MeterSequence

>>> from music21 import *
⁠
>>> a = MeterSequence('4/4')
>>> a.offsetToIndex(.5)
0
>>> a.offsetToIndex(3.5)
0
>>> a.partition(4)
>>> a.offsetToIndex(0.5)
0
>>> a.offsetToIndex(3.5)
3
>>> a.partition([1,2,1])
>>> len(a)
3
>>> a.offsetToIndex(2.9)
1
>>> a[a.offsetToIndex(2.9)]
<MeterTerminal 2/4>

>>> a = meter.MeterSequence('4/4')
>>> a.offsetToIndex(5)
Traceback (most recent call last):
...
MeterException: cannot access from qLenPos 5 where total duration is 4.0

offsetToSpan(qLenPos, permitMeterModulus=False)

Given a lenPos, return the span of the active region. Only applies to the top most level of partitions

If permitMeterModulus is True, quarter length positions greater than the duration of the Meter will be accepted as the modulus of the total meter duration.

>>> from music21 import *
>>> a = meter.MeterSequence('3/4', 3)
>>> a.offsetToSpan(.5)
(0, 1.0)
>>> a.offsetToSpan(1.5)
(1.0, 2.0)

This is the same as 1.5:

>>> a.offsetToSpan(4.5, permitMeterModulus=True)
(1.0, 2.0)

offsetToWeight(qLenPos)

Given a lenPos, return the weight of the active region. Only applies to the top-most level of partitions

>>> from music21 import *
>>> a = meter.MeterSequence('3/4', 3)
>>> a.offsetToWeight(0.0)
0.3333333333333333...
>>> a.offsetToWeight(1.5)
0.3333333333333333...

??? Not sure what this does...

partition(value)

Partitioning creates and sets a number of MeterTerminals that make up this MeterSequence.

A simple way to partition based on argument time. Single integers are treated as beat counts; lists are treated as numerator lists; MeterSequence objects are partitioned by calling partitionByOtherMeterSequence().

>>> from music21 import *
>>> a = meter.MeterSequence('5/4+3/8')
>>> len(a)
2
>>> str(a)
'{5/4+3/8}'
⁠
>>> b = meter.MeterSequence('13/8')
>>> len(b)
1
>>> str(b)
'{13/8}'
>>> b.partition(13)
>>> len(b)
13
>>> str(b)
'{1/8+1/8+1/8+...+1/8}'

>>> a.partition(b)
>>> len(a)
13
>>> str(a)
'{1/8+1/8+1/8+...+1/8}'

partitionByCount(countRequest, loadDefault=True)

Divide the current MeterSequence into the requested number of parts.

If it is not possible to divide it into the requested number, and loadDefault is True, then give the default partition:

This will destroy any established structure in the stored partition.

>>> from music21 import *
>>> a = meter.MeterSequence('4/4')
>>> a.partitionByCount(2)
>>> str(a)
'{1/2+1/2}'
>>> a.partitionByCount(4)
>>> str(a)
'{1/4+1/4+1/4+1/4}'

The partitions are not guaranteed to be the same length if the meter is irregular:

>>> b = meter.MeterSequence('5/8')
>>> b.partitionByCount(2)
>>> str(b)
'{2/8+3/8}'

This relies on a pre-defined exemption for partitioning 5 by 3:

>>> b.partitionByCount(3)
>>> str(b)
'{2/8+2/8+1/8}'

Here we use loadDefault = True to get the default:

>>> a = meter.MeterSequence('5/8')
>>> a.partitionByCount(11)
>>> str(a)
'{2/8+3/8}'

If loadDefault is False then an error is raised:

>>> a.partitionByCount(11, loadDefault = False)
Traceback (most recent call last):
MeterException: Cannot set partition by 11 (5/8)

partitionByList(numeratorList)

Given a numerator list, partition MeterSequence into a new list of MeterTerminals

>>> from music21 import *
>>> a = meter.MeterSequence('4/4')
>>> a.partitionByList([1,1,1,1])
>>> str(a)
'{1/4+1/4+1/4+1/4}'

This divides it into two equal parts:

>>> a.partitionByList([1,1])
>>> str(a)
'{1/2+1/2}'

And now into one big part:

>>> a.partitionByList([1])
>>> str(a)
'{1/1}'

Here we divide 4/4 very unconventionally:

>>> a.partitionByList(['3/4', '1/8', '1/8'])
>>> a
<MeterSequence {3/4+1/8+1/8}>

But the basics of the MeterSequence must be observed:

>>> a.partitionByList(['3/4', '1/8', '5/8'])
Traceback (most recent call last):
MeterException: Cannot set partition by ['3/4', '1/8', '5/8']

partitionByOtherMeterSequence(other)

Set partition to that found in another MeterSequence

>>> from music21 import *
>>> a = meter.MeterSequence('4/4', 4)
>>> str(a)
'{1/4+1/4+1/4+1/4}'
⁠
>>> b = meter.MeterSequence('4/4', 2)
>>> a.partitionByOtherMeterSequence(b)
>>> len(a)
2
>>> str(a)
'{1/2+1/2}'

setLevelWeight(weightList, level=0)

The weightList is an array of weights to be applied to a single level of the MeterSequence.

>>> from music21 import *
>>> a = meter.MeterSequence('4/4', 4)
>>> a.setLevelWeight([1, 2, 3, 4])
>>> a.getLevelWeight()
[1, 2, 3, 4]
⁠
>>> b = meter.MeterSequence('4/4', 4)
>>> b.setLevelWeight([2, 3])
>>> b.getLevelWeight(0)
[2, 3, 2, 3]

>>> b[1] = b[1].subdivide(2)
>>> b[3] = b[3].subdivide(2)
>>> b.getLevelWeight(0)
[2, 3.0, 2, 3.0]
⁠
>>> b[3][0] = b[3][0].subdivide(2)
>>> b
<MeterSequence {1/4+{1/8+1/8}+1/4+{{1/16+1/16}+1/8}}>
>>> b.getLevelWeight(0)
[2, 3.0, 2, 3.0]
>>> b.getLevelWeight(1)
[2, 1.5, 1.5, 2, 1.5, 1.5]
>>> b.getLevelWeight(2)
[2, 1.5, 1.5, 2, 0.75, 0.75, 1.5]

subdivideNestedHierarchy(depth, firstPartitionForm=None, normalizeDenominators=True)

Create nested structure down to a specified depth; the first division is set to one; the second division may be by 2 or 3; remaining divisions are always by 2.

This a destructive procedure that will remove any existing partition structures.

normalizeDenominators, if True, will reduce all denominators to the same minimum level.

>>> from music21 import *
>>> ms = meter.MeterSequence('4/4')
>>> ms.subdivideNestedHierarchy(1)
>>> ms
<MeterSequence {{1/2+1/2}}>
>>> ms.subdivideNestedHierarchy(2)
>>> ms
<MeterSequence {{{1/4+1/4}+{1/4+1/4}}}>
>>> ms.subdivideNestedHierarchy(3)
>>> ms
<MeterSequence {{{{1/8+1/8}+{1/8+1/8}}+{{1/8+1/8}+{1/8+1/8}}}}>
>>> ms.subdivideNestedHierarchy(4)
>>> ms
<MeterSequence {{{{{1/16+1/16}+{1/16+1/16}}+{{1/16+1/16}+{1/16+1/16}}}+{{{1/16+1/16}+{1/16+1/16}}+{{1/16+1/16}+{1/16+1/16}}}}}>
>>> ms.subdivideNestedHierarchy(5)
>>> ms
<MeterSequence {{{{{{1/32+1/32}+{1/32+1/32}}+{{1/32+1/32}+{1/32+1/32}}}+{{{1/32+1/32}+{1/32+1/32}}+{{1/32+1/32}+{1/32+1/32}}}}+{{{{1/32+1/32}+{1/32+1/32}}+{{1/32+1/32}+{1/32+1/32}}}+{{{1/32+1/32}+{1/32+1/32}}+{{1/32+1/32}+{1/32+1/32}}}}}}>

The effects above are not cumulative. Users can skip directly to whatever level of hierarchy they want.

>>> ms2 = meter.MeterSequence('4/4')
>>> ms2.subdivideNestedHierarchy(3)
>>> ms2
<MeterSequence {{{{1/8+1/8}+{1/8+1/8}}+{{1/8+1/8}+{1/8+1/8}}}}>

subdividePartitionsEqual(divisions=None)

Subdivide all partitions by equally-spaced divisions, given a divisions value. Manipulates this MeterSequence in place.

Divisions value may optionally be a MeterSequence, from which a top-level partitioning structure is derived.

>>> from music21 import *
>>> ms = meter.MeterSequence('2/4')
>>> ms.partition(2)
>>> ms
<MeterSequence {1/4+1/4}>
>>> ms.subdividePartitionsEqual(2)
>>> ms
<MeterSequence {{1/8+1/8}+{1/8+1/8}}>
>>> ms[0].subdividePartitionsEqual(2)
>>> ms
<MeterSequence {{{1/16+1/16}+{1/16+1/16}}+{1/8+1/8}}>
>>> ms[1].subdividePartitionsEqual(2)
>>> ms
<MeterSequence {{{1/16+1/16}+{1/16+1/16}}+{{1/16+1/16}+{1/16+1/16}}}>
⁠
>>> ms = meter.MeterSequence('2/4+3/4')
>>> ms.subdividePartitionsEqual(None)

Methods inherited from MeterTerminal: ratioEqual(), subdivide(), subdivideByCount(), subdivideByList(), subdivideByOther()

MeterTerminal

class music21.meter.MeterTerminal(slashNotation=None, weight=1)

A MeterTerminal is a nestable primitive of rhythmic division

>>> from music21 import *
>>> a = meter.MeterTerminal('2/4')
>>> a.duration.quarterLength
2.0
>>> a = meter.MeterTerminal('3/8')
>>> a.duration.quarterLength
1.5
>>> a = meter.MeterTerminal('5/2')
>>> a.duration.quarterLength
10.0

MeterTerminal properties

denominator

No documentation.

depth

Return how many levels deep this part is. Depth of a terminal is always 1

duration

duration gets or sets a duration value that is equal in length to the totalLength

>>> from music21 import *
>>> a = meter.MeterTerminal()
>>> a.numerator = 3
>>> a.denominator = 8
>>> d = a.duration
>>> d.type
'quarter'
>>> d.dots
1
>>> d.quarterLength
1.5

numerator

No documentation.

weight

No documentation.

MeterTerminal methods

ratioEqual(other)

Compare the numerator and denominator of another object. Note that these have to be exact matches; 3/4 is not the same as 6/8

>>> from music21 import meter
>>> a = meter.MeterTerminal('3/4')
>>> b = meter.MeterTerminal('6/4')
>>> c = meter.MeterTerminal('2/4')
>>> d = meter.MeterTerminal('3/4')
>>> a.ratioEqual(b)
False
>>> a.ratioEqual(c)
False
>>> a.ratioEqual(d)
True

subdivide(value)

Subdivision takes a MeterTerminal and, making it into a a collection of MeterTerminals, Returns a MeterSequence.

This is different than a partitioning a MeterSequence in that this does not happen in place and instead returns a new object.

If an integer is provided, assume it is a partition count

subdivideByCount(countRequest=None)

returns a MeterSequence made up of taking this MeterTerminal and subdividing it into the given number of parts. Each of those parts is a MeterTerminal

>>> from music21 import *
>>> a = meter.MeterTerminal('3/4')
>>> b = a.subdivideByCount(3)
>>> isinstance(b, meter.MeterSequence)
True
>>> len(b)
3
>>> b[0]
<MeterTerminal 1/4>

What happens if we do this?

>>> a = meter.MeterTerminal('5/8')
>>> b = a.subdivideByCount(2)
>>> isinstance(b, meter.MeterSequence)
True
>>> len(b)
2
>>> b[0]
<MeterTerminal 2/8>
>>> b[1]
<MeterTerminal 3/8>

But what if you want to divide into 3/8+2/8 or something else? for that, see the load() method of MeterSequence.

subdivideByList(numeratorList)

Return a MeterSequence dividing this MeterTerminal according to the numeratorList

>>> from music21 import *
>>> a = meter.MeterTerminal('3/4')
>>> b = a.subdivideByList([1,1,1])
>>> len(b)
3
>>> b[0]
<MeterTerminal 1/4>

Unequal subdivisions work:

>>> c = a.subdivideByList([1,2])
>>> len(c)
2
>>> (c[0], c[1])
(<MeterTerminal 1/4>, <MeterTerminal 2/4>)

So does subdividing by strings

>>> c = a.subdivideByList(['2/4', '1/4'])
>>> len(c)
2
>>> (c[0], c[1])
(<MeterTerminal 2/4>, <MeterTerminal 1/4>)

See partitionByList() method of MeterSequence for more details.

subdivideByOther(other)

Return a MeterSequence based on another MeterSequence

>>> from music21 import *
>>> a = meter.MeterSequence('1/4+1/4+1/4')
>>> a
<MeterSequence {1/4+1/4+1/4}>
>>> b = meter.MeterSequence('3/8+3/8')
>>> a.subdivideByOther(b)
<MeterSequence {{3/8+3/8}}>

NonPowerOfTwoTimeSignature

Inherits from: TimeSignature, Music21Object

class music21.meter.NonPowerOfTwoTimeSignature(value='4/4', partitionRequest=None)