music21.meter.core

This module defines two component objects for defining nested metrical structures: MeterTerminal and MeterSequence.

MeterSequence

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

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

MeterSequence bases

MeterSequence read-only properties

MeterSequence.denominator
MeterSequence.depth

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

MeterSequence.flat

Return a new MeterSequence composed of the flattened representation.

>>> ms = meter.MeterSequence('3/4', 3)
>>> b = ms.flat
>>> len(b)
3

>>> ms[1] = ms[1].subdivide(4)
>>> b = ms.flat
>>> len(b)
6

>>> ms[1][2] = ms[1][2].subdivide(4)
>>> ms
<music21.meter.core.MeterSequence {1/4+{1/16+1/16+{1/64+1/64+1/64+1/64}+1/16}+1/4}>
>>> b = ms.flat
>>> len(b)
9
MeterSequence.flatWeight

Return a list of flat weight values

MeterSequence.numerator
MeterSequence.partitionDisplay

Property – Display the partition as a str without the surrounding curly brackets.

>>> a = meter.MeterSequence('4/4')
>>> a.partitionDisplay
'4/4'
>>> a = meter.MeterSequence('2/4+6/8')
>>> a.partitionDisplay
'2/4+6/8'

partitionDisplay is most useful for non-divided meter sequences. This is less helpful:

>>> a = meter.MeterSequence('4/4', 4)
>>> a.partitionDisplay
'1/4+1/4+1/4+1/4'
MeterSequence.partitionStr

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

>>> ms = meter.MeterSequence('2/4+2/4')
>>> ms
<music21.meter.core.MeterSequence {2/4+2/4}>
>>> ms.partitionStr
'Duple'

>>> ms = meter.MeterSequence('6/4', 6)
>>> ms
<music21.meter.core.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'

Anything larger than 8 is simply the number followed by ‘-uple’

>>> ms = meter.MeterSequence('13/4', 13)
>>> ms.partitionStr
'13-uple'

Single partition:

>>> ms = meter.MeterSequence('3/4', 1)
>>> ms.partitionStr
'Single'

Read-only properties inherited from ProtoM21Object:

MeterSequence read/write properties

MeterSequence.weight

Get or set the weight for each object in this MeterSequence

>>> a = meter.MeterSequence('3/4')
>>> a.partition(3)
>>> a.weight = 1
>>> a[0].weight
0.333...
>>> b = meter.MeterTerminal('1/4', 0.25)
>>> c = meter.MeterTerminal('1/4', 0.25)
>>> d = meter.MeterSequence([b, c])
>>> d.weight
0.5

Assume this MeterSequence is a whole, not a part of some larger MeterSequence. Thus, we cannot use numerator/denominator relationship as a scalar.

Read/write properties inherited from MeterTerminal:

MeterSequence methods

MeterSequence.__getitem__(key)

Get an MeterTerminal from _partition

>>> a = meter.MeterSequence('4/4', 4)
>>> a[3].numerator
1
MeterSequence.getLevel(level=0, flat=True)

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

>>> 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
<music21.meter.core.MeterSequence {1/4+{1/8+1/8}+1/4+{{1/16+1/16}+1/8}}>
>>> b.getLevel(0)
<music21.meter.core.MeterSequence {1/4+1/4+1/4+1/4}>
>>> b.getLevel(1)
<music21.meter.core.MeterSequence {1/4+1/8+1/8+1/4+1/8+1/8}>
>>> b.getLevel(2)
<music21.meter.core.MeterSequence {1/4+1/8+1/8+1/4+1/16+1/16+1/8}>
MeterSequence.getLevelList(levelCount, flat=True)

Recursive utility function that gets everything at a certain level.

>>> 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
<music21.meter.core.MeterSequence {1/4+{1/8+1/8}+1/4+{{1/16+1/16}+1/8}}>
>>> b.getLevelList(0)
[<music21.meter.core.MeterTerminal 1/4>,
 <music21.meter.core.MeterTerminal 1/4>,
 <music21.meter.core.MeterTerminal 1/4>,
 <music21.meter.core.MeterTerminal 1/4>]
>>> meter.MeterSequence(b.getLevelList(0))
<music21.meter.core.MeterSequence {1/4+1/4+1/4+1/4}>
>>> meter.MeterSequence(b.getLevelList(1))
<music21.meter.core.MeterSequence {1/4+1/8+1/8+1/4+1/8+1/8}>
>>> meter.MeterSequence(b.getLevelList(2))
<music21.meter.core.MeterSequence {1/4+1/8+1/8+1/4+1/16+1/16+1/8}>
>>> meter.MeterSequence(b.getLevelList(3))
<music21.meter.core.MeterSequence {1/4+1/8+1/8+1/4+1/16+1/16+1/8}>
MeterSequence.getLevelSpan(level=0)

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

>>> 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
<music21.meter.core.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)]
MeterSequence.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

>>> 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
<music21.meter.core.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]
MeterSequence.getPartitionOptions() → Tuple[Tuple[str, ...], ...]

Return either a cached or a new set of division/partition options.

Calls tools.divisionOptionsAlgo and tools.divisionOptionsPreset (which will be empty except if the numerator is 5).

Works on anything that has a .numerator and .denominator.

>>> meter.MeterSequence('3/4').getPartitionOptions()
(('1/4', '1/4', '1/4'),
 ('1/8', '1/8', '1/8', '1/8', '1/8', '1/8'),
 ('1/16', '1/16', '1/16', '1/16', '1/16', '1/16', '1/16',
  '1/16', '1/16', '1/16', '1/16', '1/16'),
 ('3/4',), ('6/8',), ('12/16',), ('24/32',), ('48/64',), ('96/128',))

The additional 2 + 2 + 1 and 2 + 1 + 2 options for numerator 5 are at the end.

>>> meter.MeterSequence('5/32').getPartitionOptions()
(('2/32', '3/32'),
 ('3/32', '2/32'),
 ('1/32', '1/32', '1/32', '1/32', '1/32'),
 ('1/64', '1/64', '1/64', '1/64', '1/64',
  '1/64', '1/64', '1/64', '1/64', '1/64'),
 ('5/32',), ('10/64',), ('20/128',),
 ('2/32', '2/32', '1/32'), ('2/32', '1/32', '2/32'))
MeterSequence.isUniformPartition(*, depth=0)

Return True if the top-level partitions (if depth=0) or a lower-level section has equal durations

>>> ms = meter.MeterSequence('3/8+2/8+3/4')
>>> ms.isUniformPartition()
False
>>> ms = meter.MeterSequence('4/4')
>>> ms.isUniformPartition()
True
>>> ms.partition(4)
>>> ms.isUniformPartition()
True
>>> ms[0] = ms[0].subdivideByCount(2)
>>> ms[1] = ms[1].subdivideByCount(4)
>>> ms.isUniformPartition()
True
>>> ms.isUniformPartition(depth=1)
False

>>> 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

Changed in v7 – depth is keyword only

MeterSequence.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. targetWeight, if given, will be used instead of self.weight

loading is a destructive operation.

>>> 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}'
MeterSequence.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.

>>> a = meter.MeterSequence('3/4', 3)
>>> a[1] = a[1].subdivide(4)
>>> a
<music21.meter.core.MeterSequence {1/4+{1/16+1/16+1/16+1/16}+1/4}>
>>> len(a)
3
>>> a.offsetToAddress(0.5)
[0]
>>> a[0]
<music21.meter.core.MeterTerminal 1/4>
>>> a.offsetToAddress(1.0)
[1, 0]
>>> a.offsetToAddress(1.5)
[1, 2]
>>> a[1][2]
<music21.meter.core.MeterTerminal 1/16>
>>> a.offsetToAddress(1.99)
[1, 3]
>>> a.offsetToAddress(2.5)
[2]
MeterSequence.offsetToDepth(qLenPos, align='quantize', index: int | None = None)

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

>>> 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
<music21.meter.core.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

>>> b.offsetToDepth(-1)
Traceback (most recent call last):
music21.exceptions21.MeterException: cannot access from qLenPos -1.0

Changed in v.7 – index can be provided, if known, for a long MeterSequence to improve performance.

MeterSequence.offsetToIndex(qLenPos, includeCoincidentBoundaries=False) → int

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

>>> a = meter.MeterSequence('4/4')
>>> a.offsetToIndex(0.5)
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)]
<music21.meter.core.MeterTerminal 2/4>

>>> a = meter.MeterSequence('4/4')
>>> a.offsetToIndex(5.0)
Traceback (most recent call last):
music21.exceptions21.MeterException: cannot access from qLenPos 5.0
    where total duration is 4.0

Negative numbers also raise an exception:

>>> a.offsetToIndex(-0.5)
Traceback (most recent call last):
music21.exceptions21.MeterException: cannot access from qLenPos -0.5
    where total duration is 4.0
MeterSequence.offsetToSpan(qLenPos, permitMeterModulus=False)

Given a qLenPos, 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.

>>> a = meter.MeterSequence('3/4', 3)
>>> a.offsetToSpan(0.5)
(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)

Make sure it works for tuplets even with so-so rounding:

>>> a.offsetToSpan(4.33333336, permitMeterModulus=True)
(1.0, 2.0)
MeterSequence.offsetToWeight(qLenPos)

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

>>> a = meter.MeterSequence('3/4', 3)
>>> a.offsetToWeight(0.0)
Fraction(1, 3)
>>> a.offsetToWeight(1.5)
Fraction(1, 3)

??? Not sure what this does…

MeterSequence.partition(value, loadDefault=False)

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().

>>> 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}'

Demo of loadDefault: if impossible, then do it another way…

>>> c = meter.MeterSequence('3/128')
>>> c.partition(2)
Traceback (most recent call last):
music21.exceptions21.MeterException: Cannot set partition by 2 (3/128)

>>> c = meter.MeterSequence('3/128')
>>> c.partition(2, loadDefault=True)
>>> len(c)
3
>>> str(c)
'{1/128+1/128+1/128}'
MeterSequence.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.

>>> a = meter.MeterSequence('4/4')
>>> a
<music21.meter.core.MeterSequence {4/4}>
>>> a.partitionByCount(2)
>>> a
<music21.meter.core.MeterSequence {1/2+1/2}>
>>> str(a)
'{1/2+1/2}'
>>> a.partitionByCount(4)
>>> a
<music21.meter.core.MeterSequence {1/4+1/4+1/4+1/4}>
>>> 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)
>>> b
 <music21.meter.core.MeterSequence {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 partition in case there is no known way to do this:

>>> 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):
music21.exceptions21.MeterException: Cannot set partition by 11 (5/8)
MeterSequence.partitionByList(numeratorList)

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

>>> 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
<music21.meter.core.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):
music21.exceptions21.MeterException: Cannot set partition by ['3/4', '1/8', '5/8']
MeterSequence.partitionByOtherMeterSequence(other)

Set partition to that found in another MeterSequence

>>> 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}'
MeterSequence.setLevelWeight(weightList, level=0)

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

>>> 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
<music21.meter.core.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]
MeterSequence.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.

>>> ms = meter.MeterSequence('4/4')
>>> ms.subdivideNestedHierarchy(1)
>>> ms
<music21.meter.core.MeterSequence {{1/2+1/2}}>
>>> ms.subdivideNestedHierarchy(2)
>>> ms
<music21.meter.core.MeterSequence {{{1/4+1/4}+{1/4+1/4}}}>
>>> ms.subdivideNestedHierarchy(3)
>>> ms
<music21.meter.core.MeterSequence {{{{1/8+1/8}+{1/8+1/8}}+{{1/8+1/8}+{1/8+1/8}}}}>

I think you get the picture…

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
<music21.meter.core.MeterSequence {{{{1/8+1/8}+{1/8+1/8}}+{{1/8+1/8}+{1/8+1/8}}}}>
MeterSequence.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.

>>> ms = meter.MeterSequence('2/4')
>>> ms.partition(2)
>>> ms
<music21.meter.core.MeterSequence {1/4+1/4}>
>>> ms.subdividePartitionsEqual(2)
>>> ms
<music21.meter.core.MeterSequence {{1/8+1/8}+{1/8+1/8}}>
>>> ms[0].subdividePartitionsEqual(2)
>>> ms
<music21.meter.core.MeterSequence {{{1/16+1/16}+{1/16+1/16}}+{1/8+1/8}}>
>>> ms[1].subdividePartitionsEqual(2)
>>> ms
<music21.meter.core.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)
>>> ms
<music21.meter.core.MeterSequence {{1/4+1/4}+{1/4+1/4+1/4}}>

Methods inherited from MeterTerminal:

Methods inherited from ProtoM21Object:

MeterTerminal

class music21.meter.core.MeterTerminal(slashNotation: str | None = None, weight=1)

A MeterTerminal is a nestable primitive of rhythmic division.

>>> 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 bases

MeterTerminal read-only properties

MeterTerminal.depth

Return how many levels deep this part is – the depth of a terminal is always 1

Read-only properties inherited from ProtoM21Object:

MeterTerminal read/write properties

MeterTerminal.denominator
MeterTerminal.duration

duration gets or sets a duration value that is equal in length of the terminal.

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

Return or set the weight of a MeterTerminal

>>> a = meter.MeterTerminal('2/4')
>>> a.weight = 0.5
>>> a.weight
0.5

MeterTerminal methods

MeterTerminal.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

>>> 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
MeterTerminal.subdivide(value)

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

This is different from partitioning a MeterSequence. subdivide does not happen in place and instead returns a new object.

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

MeterTerminal.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

>>> a = meter.MeterTerminal('3/4')
>>> b = a.subdivideByCount(3)
>>> b
<music21.meter.core.MeterSequence {1/4+1/4+1/4}>
>>> len(b)
3
>>> b[0]
<music21.meter.core.MeterTerminal 1/4>

What happens if we do this?

>>> a = meter.MeterTerminal('5/8')
>>> b = a.subdivideByCount(2)
>>> b
<music21.meter.core.MeterSequence {2/8+3/8}>
>>> len(b)
2
>>> b[0]
<music21.meter.core.MeterTerminal 2/8>
>>> b[1]
<music21.meter.core.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.

MeterTerminal.subdivideByList(numeratorList)

Return a MeterSequence dividing this MeterTerminal according to the numeratorList

>>> a = meter.MeterTerminal('3/4')
>>> b = a.subdivideByList([1, 1, 1])
>>> b
<music21.meter.core.MeterSequence {1/4+1/4+1/4}>
>>> len(b)
3
>>> b[0]
<music21.meter.core.MeterTerminal 1/4>

Unequal subdivisions work:

>>> c = a.subdivideByList([1, 2])
>>> c
<music21.meter.core.MeterSequence {1/4+2/4}>
>>> len(c)
2
>>> (c[0], c[1])
(<music21.meter.core.MeterTerminal 1/4>, <music21.meter.core.MeterTerminal 2/4>)

So does subdividing by strings

>>> c = a.subdivideByList(['2/4', '1/4'])
>>> len(c)
2
>>> (c[0], c[1])
(<music21.meter.core.MeterTerminal 2/4>, <music21.meter.core.MeterTerminal 1/4>)

See partitionByList() method of MeterSequence for more details.

MeterTerminal.subdivideByOther(other: music21.meter.MeterSequence)

Return a MeterSequence based on another MeterSequence

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

>>> terminal = meter.MeterTerminal('1/4')
>>> divider = meter.MeterSequence('1/8+1/8')
>>> terminal.subdivideByOther(divider)
<music21.meter.core.MeterSequence {{1/8+1/8}}>

Methods inherited from ProtoM21Object: