music21.tree.spans

Tools for grouping notes and chords into a searchable tree organized by start and stop offsets.

ElementTimespan

class music21.tree.spans.ElementTimespan(element=None, parentOffset=None, parentEndTime=None, parentage=None, offset=None, endTime=None)

A span of time anchored to an element in a score. The span of time may be the same length as the element in the score. It may be shorter (a “slice” of an element) or it may be longer (in the case of a timespan that is anchored to a single element but extends over rests or other notes following a note)

PitchedTimespans give information about an element (such as a Note). It knows its absolute position with respect to the element passed into TimespanTree. It contains information about what measure it’s in, what part it’s in, etc.

Example, getting a passing tone from a known location from a Bach chorale.

First we create an Offset tree:

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans()
>>> scoreTree
<TimespanTree {195} (0.0 to 36.0) <music21.stream.Score ...>>

Then get the verticality from offset 6.5, which is beat two-and-a-half of measure 2 (the piece is in 4/4 with a quarter-note pickup)

>>> verticality = scoreTree.getVerticalityAt(6.5)
>>> verticality
<Verticality 6.5 {E3 D4 G#4 B4}>

There are four PitchedTimespans in the verticality – each representing a note. The notes are arranged from lowest to highest.

We can find all the PitchedTimespans that start exactly at 6.5. There’s one.

>>> verticality.startTimespans
(<PitchedTimespan (6.5 to 7.0) <music21.note.Note D>>,)
>>> pitchedTimespan = verticality.startTimespans[0]
>>> pitchedTimespan
<PitchedTimespan (6.5 to 7.0) <music21.note.Note D>>

What can we do with a PitchedTimespan? We can get its Part object and from there the Part object name

>>> pitchedTimespan.part
<music21.stream.Part Tenor>
>>> pitchedTimespan.part.partName
'Tenor'

Find out what measure it’s in:

>>> pitchedTimespan.measureNumber
2
>>> pitchedTimespan.parentOffset
5.0

The position in the measure is given by subtracting that from the .offset:

>>> pitchedTimespan.offset - pitchedTimespan.parentOffset
1.5
>>> pitchedTimespan.element
<music21.note.Note D>

These are not dynamic, so changing the Score object does not change the measureNumber, etc.

ElementTimespan bases

ElementTimespan read-only properties

ElementTimespan.measureNumber

The measure number of the measure containing the element.

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans()
>>> verticality = scoreTree.getVerticalityAt(1.0)
>>> pitchedTimespan = verticality.startTimespans[0]
>>> pitchedTimespan.measureNumber
1
ElementTimespan.part

find the object in the parentage that is a Part object:

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans()
>>> verticality = scoreTree.getVerticalityAt(1.0)
>>> pitchedTimespan = verticality.startTimespans[2]
>>> pitchedTimespan
<PitchedTimespan (1.0 to 2.0) <music21.note.Note C#>>
>>> pitchedTimespan.part
<music21.stream.Part Tenor>
ElementTimespan.quarterLength

The quarterLength of the Timespan, which, due to manipulation, may be different from that of the element.

>>> n = note.Note('D-')
>>> n.offset = 1.0
>>> n.duration.quarterLength = 2.0
>>> pts = tree.spans.PitchedTimespan(n, offset=n.offset, endTime=3.0)
>>> pts
<PitchedTimespan (1.0 to 3.0) <music21.note.Note D->>
>>> pts.quarterLength
2.0
>>> n.duration.quarterLength
2.0
>>> pts2 = pts.new(offset=0.0)
>>> pts2
<PitchedTimespan (0.0 to 3.0) <music21.note.Note D->>
>>> pts2.quarterLength
3.0
>>> pts2.element.duration.quarterLength
2.0

Read-only properties inherited from Timespan:

ElementTimespan methods

ElementTimespan.getParentageByClass(classList)

returns that is the first parentage that has this classList. default stream.Part

>>> score = corpus.parse('bwv66.6')
>>> score.id = 'bach'
>>> scoreTree = score.asTimespans()
>>> verticality = scoreTree.getVerticalityAt(1.0)
>>> pitchedTimespan = verticality.startTimespans[2]
>>> pitchedTimespan
<PitchedTimespan (1.0 to 2.0) <music21.note.Note C#>>
>>> pitchedTimespan.getParentageByClass(classList=(stream.Part,))
<music21.stream.Part Tenor>
>>> pitchedTimespan.getParentageByClass(classList=(stream.Measure,))
<music21.stream.Measure 1 offset=1.0>
>>> pitchedTimespan.getParentageByClass(classList=(stream.Score,))
<music21.stream.Score bach>

The closest parent is returned in case of a multiple list…

>>> searchTuple = (stream.Voice, stream.Measure, stream.Part)
>>> pitchedTimespan.getParentageByClass(classList=searchTuple)
<music21.stream.Measure 1 offset=1.0>

TODO: this should take a normal class list.

ElementTimespan.makeElement(makeCopy=True)

Return a copy of the element (or the same one if makeCopy is False) with the quarterLength set to the length of the timespan

ElementTimespan.new(element=None, parentOffset=None, parentEndTime=None, offset=None, endTime=None)

Create a new object that is identical to the calling object but with some of the parameters overridden.

>>> n = note.Note("C#")
>>> pts = tree.spans.PitchedTimespan(n, offset=11.0, endTime=12.0)
>>> pts
<PitchedTimespan (11.0 to 12.0) <music21.note.Note C#>>
>>> pts2 = pts.new(endTime=13.0)
>>> pts2
<PitchedTimespan (11.0 to 13.0) <music21.note.Note C#>>
>>> pts.element is pts2.element
True

Methods inherited from Timespan:

ElementTimespan instance variables

ElementTimespan.parentage

The Stream hierarchy above the ElementTimespan’s element.

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans()
>>> verticality = scoreTree.getVerticalityAt(1.0)
>>> pitchedTimespan = verticality.startTimespans[0]
>>> pitchedTimespan
<PitchedTimespan (1.0 to 2.0) <music21.note.Note A>>
>>> for streamSite in pitchedTimespan.parentage:
...     streamSite
<music21.stream.Measure 1 offset=1.0>
<music21.stream.Part Soprano>
<music21.stream.Score ...>

PitchedTimespan

class music21.tree.spans.PitchedTimespan(element=None, parentOffset=None, parentEndTime=None, parentage=None, offset=None, endTime=None)

PitchedTimespan bases

PitchedTimespan read-only properties

PitchedTimespan.pitches

Gets the pitches of the element wrapped by this PitchedTimespan.

>>> c = chord.Chord('C4 E4 G4')
>>> pts = tree.spans.PitchedTimespan(c, offset=0.0, endTime=1.0)
>>> pts.pitches
(<music21.pitch.Pitch C4>, <music21.pitch.Pitch E4>, <music21.pitch.Pitch G4>)
>>> pts.pitches == c.pitches
True
>>> pts.pitches is c.pitches
False

Read-only properties inherited from ElementTimespan:

Read-only properties inherited from Timespan:

PitchedTimespan methods

PitchedTimespan.canMerge(other)

sub-method of base canMerge that checks to see if the pitches are the same.

For quick score reductions, we can merge two consecutive like-pitched element timespans, keeping score-relevant information from the first of the two, such as its Music21 Element.

This is useful when using timespans to perform score reduction.

Let’s demonstrate merging some contiguous E’s in the alto part of a Bach chorale:

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans(classList=(note.Note,))
>>> timespan_one = scoreTree[12]
>>> print(timespan_one)
<PitchedTimespan (2.0 to 3.0) <music21.note.Note E>>
>>> print(timespan_one.part)
<music21.stream.Part Alto>
>>> timespan_two = scoreTree.findNextPitchedTimespanInSameStreamByClass(timespan_one)
>>> print(timespan_two)
<PitchedTimespan (3.0 to 4.0) <music21.note.Note E>>
>>> timespan_one.canMerge(timespan_two)
(True, '')
>>> merged = timespan_one.mergeWith(timespan_two)
>>> print(merged)
<PitchedTimespan (2.0 to 4.0) <music21.note.Note E>>
>>> merged.part is timespan_one.part
True

Attempting to merge timespans which are not contiguous, or which do not have identical pitches will result in error:

>>> scoreTree[0].canMerge(scoreTree[50])
(False, 'Cannot merge <PitchedTimespan (0.0 to 0.5) <music21.note.Note C#>>
     with <PitchedTimespan (9.5 to 10.0) <music21.note.Note B>>: not contiguous')
>>> scoreTree[0].mergeWith(scoreTree[50])
Traceback (most recent call last):
music21.tree.spans.TimespanException: Cannot merge
        <PitchedTimespan (0.0 to 0.5) <music21.note.Note C#>>
        with <PitchedTimespan (9.5 to 10.0) <music21.note.Note B>>: not contiguous

This is probably not what you want to do: get the next element timespan in the same score:

>>> timespan_twoWrong = scoreTree.findNextPitchedTimespanInSameStreamByClass(
...     timespan_one, classList=(stream.Score,))
>>> print(timespan_twoWrong)
<PitchedTimespan (3.0 to 4.0) <music21.note.Note C#>>
>>> print(timespan_twoWrong.part)
<music21.stream.Part Soprano>

Methods inherited from ElementTimespan:

Methods inherited from Timespan:

PitchedTimespan instance variables

Instance variables inherited from ElementTimespan:

Timespan

class music21.tree.spans.Timespan(offset=-inf, endTime=inf)

A span of time, with a start offset and stop offset.

Useful for demonstrating various properties of the timespan-collection class family.

>>> timespan = tree.spans.Timespan(-1.5, 3.25)
>>> print(timespan)
<Timespan -1.5 3.25>

A timespan has two attributes, its offset and its endTime. They are immutable…

>>> timespan.offset
-1.5
>>> timespan.endTime
3.25

To create a changed timespan, call the .new() method on the timespan.

>>> ts2 = timespan.new(offset=0.0)
>>> ts2
<Timespan 0.0 3.25>
>>> ts3 = timespan.new(endTime=5.0)
>>> ts3
<Timespan -1.5 5.0>

Two timespans are equal if they have the same offset and endTime

>>> ts4 = tree.spans.Timespan(-1.5, 5.0)
>>> ts3 == ts4
True
>>> ts4 == ts2
False

Timespan read-only properties

Timespan.endTime

The stop offset of the Timespan, relative to its containing score.

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans()
>>> verticality = scoreTree.getVerticalityAt(1.0)
>>> timespan = verticality.startTimespans[0]
>>> timespan.endTime
2.0
Timespan.offset

The start offset of the Timespan, relative to its containing score.

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans()
>>> verticality = scoreTree.getVerticalityAt(1.0)
>>> timespan = verticality.startTimespans[0]
>>> timespan.offset
1.0

Timespan methods

Timespan.canMerge(other)

returns a tuple of (True or False) if these timespans can be merged with the second element being a message or None.

>>> ts1 = tree.spans.Timespan(0, 5)
>>> ts2 = tree.spans.Timespan(5, 7)
>>> ts1.canMerge(ts2)
(True, '')
>>> ts3 = tree.spans.Timespan(6, 10)
>>> ts1.canMerge(ts3)
(False, 'Cannot merge <Timespan 0.0 5.0> with <Timespan 6.0 10.0>: not contiguous')

Overlapping Timespans cannot be merged, just contiguous ones.

>>> ts4 = tree.spans.Timespan(3, 4)
>>> ts1.canMerge(ts4)
(False, 'Cannot merge <Timespan 0.0 5.0> with <Timespan 3.0 4.0>: not contiguous')
Timespan.mergeWith(other)

Merges two consecutive/contiguous timespans, keeping the information from the former of the two.

>>> ts1 = tree.spans.Timespan(0, 5)
>>> ts2 = tree.spans.Timespan(5, 7)
>>> ts3 = ts1.mergeWith(ts2)
>>> ts3
<Timespan 0.0 7.0>

Note that (for now), overlapping timespans cannot be merged:

>>> ts4 = tree.spans.Timespan(6, 10)
>>> ts3.mergeWith(ts4)
Traceback (most recent call last):
music21.tree.spans.TimespanException: Cannot merge <Timespan 0.0 7.0> with
    <Timespan 6.0 10.0>: not contiguous
Timespan.new(offset=None, endTime=None)

return a new object with the given offset and endTime

Timespan.splitAt(offset)

Split Timespan at offset.

>>> score = corpus.parse('bwv66.6')
>>> scoreTree = score.asTimespans(classList=(note.Note,))
>>> verticality = scoreTree.getVerticalityAt(0)
>>> verticality
<Verticality 0 {A3 E4 C#5}>
>>> timespan = verticality.startTimespans[0]
>>> timespan
<PitchedTimespan (0.0 to 0.5) <music21.note.Note C#>>
>>> for shard in timespan.splitAt(0.25):
...     shard
...
<PitchedTimespan (0.0 to 0.25) <music21.note.Note C#>>
<PitchedTimespan (0.25 to 0.5) <music21.note.Note C#>>
>>> timespan.splitAt(1000)
(<PitchedTimespan (0.0 to 0.5) <music21.note.Note C#>>,)