khodowany
71 lines
2.6 KiB
Python
71 lines
2.6 KiB
Python
"""Exact rhythmic groups for generated material; imported music is not quantized.
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Binary boundaries may be displaced together. Tuplet runs must return to their
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entry subdivision phase before binary material resumes. A search boundary is
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not a rhythmic boundary and must not be used to clip a group.
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"""
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from __future__ import annotations
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import dataclasses
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import functools
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from fractions import Fraction as F
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@dataclasses.dataclass(frozen=True)
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class RhythmGroup:
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start: F
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end: F
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family: str
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events: tuple[tuple[F, F], ...]
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displacement: F = F()
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source: str = ''
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def describe(pattern, *, origin=F(), source='', imported=False):
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if not pattern:return ()
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if imported:
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return (RhythmGroup(origin, origin+pattern[-1][1], 'source', pattern, source=source),)
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result=[]; i=0
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while i<len(pattern):
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a,b=pattern[i]
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if b<=a or i and a<pattern[i-1][1]:raise ValueError('overlapping rhythm group')
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# A complete ternary figure can be intentionally displaced on an eighth.
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if (b-a).denominator%3==0:
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if (a*2).denominator!=1:raise ValueError('unexplained tuplet entry phase')
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start=i; cursor=a
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while i<len(pattern):
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x,y=pattern[i]
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if x!=cursor or (y-x).denominator not in (3,6):break
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cursor=y;i+=1
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if (cursor-a).denominator==1:break
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if i==start or (cursor-a).denominator!=1:
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raise ValueError('incomplete tuplet group')
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group=pattern[start:i]
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result.append(RhythmGroup(origin+a,origin+cursor,'triplet',group,a%1,source))
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else:
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if (a*4).denominator!=1 or (b*4).denominator!=1:
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raise ValueError('unexplained binary subdivision phase')
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family='sixteenth' if (a*2).denominator!=1 or (b*2).denominator!=1 else 'binary'
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result.append(RhythmGroup(origin+a,origin+b,family,((a,b),),a%1,source));i+=1
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return tuple(result)
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@functools.lru_cache(maxsize=8192)
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def valid(pattern):
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try:describe(pattern);return True
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except ValueError:return False
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def signature(notes):
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"""Translation-invariant duration, inter-onset and rest vocabulary."""
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return tuple((n.end-n.start, notes[i+1].start-n.end if i+1<len(notes) else F())
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for i,n in enumerate(notes))
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def broaden(pattern, arrival, release):
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"""Reopen an editable binary tail; never slice a tuplet or inherit its phase."""
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if (arrival*2).denominator!=1 or (release*2).denominator!=1:return ()
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for group in describe(pattern):
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if group.family=='triplet' and group.start<arrival<group.end:return ()
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result=tuple((a,min(b,arrival)) for a,b in pattern if a<arrival)+((arrival,release),)
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return result if valid(result) else ()
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