Rhythm Selection & Cleanup

generator/rhythm.py

@@ -0,0 +1,95 @@
+from __future__ import annotations
+
+import dataclasses
+import fractions
+import pathlib
+import types
+
+import generator.model
+import generator.musicxml
+
+@dataclasses.dataclass(frozen=True)
+class Event:
+  onset: fractions.Fraction
+  duration: fractions.Fraction
+  sounding: bool
+  written_type: str
+  dots: int = 0
+  beams: tuple[tuple[int, str], ...] = ()
+  continuation: bool = False
+
+@dataclasses.dataclass(frozen=True)
+class Bar:
+  events: tuple[Event, ...]
+  length: fractions.Fraction
+  def attacks(self) -> tuple[fractions.Fraction, ...]:
+    return tuple(e.onset for e in self.events if e.sounding and not e.continuation)
+  def beat(self, number: int) -> tuple:
+    return tuple((max(e.onset, number) - number, min(e.onset + e.duration, number + 1) - max(e.onset, number), e.sounding, e.continuation or e.onset < number) for e in self.events if e.onset < number + 1 and e.onset + e.duration > number)
+
+@dataclasses.dataclass(frozen=True)
+class Snippet:
+  id: str
+  meter: str
+  bars: tuple[Bar, ...]
+
+@dataclasses.dataclass(frozen=True, init=False)
+class Library:
+  snippets: types.MappingProxyType
+  def __init__(self, snippets: tuple[Snippet, ...]):
+    grouped = {}
+    identities = set()
+    for snippet in sorted(snippets, key=lambda s: s.id):
+      if snippet.id in identities:
+        raise ValueError(f'duplicate rhythm identity: {snippet.id}')
+      identities.add(snippet.id)
+      grouped.setdefault(snippet.meter, []).append(snippet)
+    object.__setattr__(self, 'snippets', types.MappingProxyType({meter: tuple(values) for meter, values in grouped.items()}))
+  def for_meter(self, meter: str) -> tuple[Snippet, ...]:
+    if meter not in ('2/4', '3/4', '4/4', '5/4') or meter not in self.snippets:
+      raise ValueError(f'accompaniment requires rhythm snippets for {meter}; supported meters are 2/4, 3/4, 4/4, and 5/4')
+    return self.snippets[meter]
+
+def read_snippet(path: pathlib.Path, identifier: str) -> Snippet:
+  document = generator.musicxml.load_musicxml(path)
+  staff = document['staves'][0]
+  if len(staff['measures']) not in (1, 2) or staff.get('tuplets'):
+    raise ValueError(f'{path}: rhythm snippets require one or two bars without tuplets')
+  meter = staff['measures'][0]['time_signature']
+  bars = []
+  for measure in staff['measures']:
+    length = generator.model.fraction(measure['duration'])
+    if measure['time_signature'] != meter or length != generator.model.meter_length(measure['meter']):
+      raise ValueError(f'{path}, measure {measure["number"]}: rhythm bars must be complete and use one meter')
+    if len(measure['voices']) != 1 or any('meter' in a for a in measure.get('attributes', [])):
+      raise ValueError(f'{path}: rhythm snippets require one voice without meter changes')
+    events = []
+    cursor = fractions.Fraction()
+    for note in measure['voices'][0]['notes']:
+      onset, duration = generator.model.fraction(note['onset']), generator.model.fraction(note['duration'])
+      if onset != cursor or duration <= 0 or note.get('grace') or note['kind'] not in ('note', 'rest') or note.get('tremolo'):
+        raise ValueError(f'{path}, measure {measure["number"]}: rhythm events must fill the bar sequentially')
+      if 'ratio' in note['written']:
+        raise ValueError(f'{path}, measure {measure["number"]}: rhythm snippets do not support time modifications')
+      events.append(Event(onset, duration, note['kind'] == 'note', note['written']['type'], note['written'].get('dots', 0), tuple((b['level'], b['type']) for b in note.get('beams', [])), any('tie_from' in p for p in note['pitches'])))
+      cursor += duration
+    if cursor != length:
+      raise ValueError(f'{path}: rhythm events do not fill the bar')
+    bars.append(Bar(tuple(events), length))
+  return Snippet(identifier, meter, tuple(bars))
+
+def load_library(root: pathlib.Path) -> Library:
+  if not root.is_dir():
+    raise ValueError(f'{root}: rhythm library not found')
+  snippets = []
+  for path in sorted(root.rglob('*.xml')):
+    relative = path.relative_to(root)
+    if len(relative.parts) != 3 or relative.parts[0] not in ('2-4', '3-4', '4-4', '5-4') or relative.parts[1] not in ('1', '2'):
+      raise ValueError(f'{path}: rhythm sources belong under meter/series')
+    snippet = read_snippet(path, relative.as_posix())
+    if snippet.meter != relative.parts[0].replace('-', '/'):
+      raise ValueError(f'{path}: rhythm meter disagrees with its directory')
+    snippets.append(snippet)
+  if not snippets:
+    raise ValueError(f'{root}: rhythm library is empty')
+  return Library(tuple(snippets))