Tab Generation

generator/scat.py

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+from __future__ import annotations
+
+from fractions import Fraction
+
+from generator.model import beat_lengths, fraction, rational
+
+def pulse(measure: dict, onset: Fraction) -> tuple[Fraction | None, bool]:
+  start, meter = Fraction(), measure['meter']
+  for change in measure.get('attributes', []):
+    if fraction(change['onset']) <= onset and 'meter' in change:
+      start, meter = fraction(change['onset']), change['meter']
+  beats = beat_lengths(meter)
+  if not beats:
+    return None, False
+  # Pickups occupy the final beats of their meter.
+  phase = onset - start
+  if measure.get('implicit') and not start:
+    phase += max(Fraction(), sum(beats) - fraction(measure['duration']))
+  phase %= sum(beats)
+  for beat in beats:
+    if phase < beat:
+      return beat, phase == 0
+    phase -= beat
+  raise ValueError('invalid meter pulse')
+
+def syllable(duration: Fraction, beat: Fraction | None, onbeat: bool, final: bool, previous: str) -> str:
+  if duration >= (beat if beat is not None else 1):
+    return 'doo'
+  if final:
+    return 'dat'
+  result = 'dit' if beat is not None and not onbeat else 'ba'
+  return 'da' if result == previous else result
+
+def add_scat(document: dict) -> None:
+  events, pitches = [], {}
+  absolute = Fraction()
+  boundaries = set()
+  for measure in document['staves'][0]['measures']:
+    if measure.get('section_label'):
+      boundaries.add(absolute)
+    for voice in measure['voices']:
+      for note in voice['notes']:
+        for field in ('lyrics', 'lyric', 'lyric_notation'):
+          note.pop(field, None)
+        onset = absolute + fraction(note['onset'])
+        for tone in note['pitches']:
+          pitches[tone['id']] = (note, tone, onset)
+        events.append((note, measure, onset))
+    absolute += fraction(measure['duration'])
+  attacks = [(n, m, t) for n, m, t in events if n['pitches'] and not n.get('cue') and not n['pitches'][0].get('cue') and not n['pitches'][0].get('tie_from')]
+  previous, previous_end = '', None
+  for index, (note, measure, onset) in enumerate(attacks):
+    tone = note['pitches'][0]
+    end = onset + fraction(tone['duration'])
+    chain = []
+    while target := tone.get('tie_to'):
+      continuation, tone, time = pitches[target]
+      chain.append(continuation)
+      end = time + fraction(tone['duration'])
+    following = attacks[index + 1][2] if index + 1 < len(attacks) else None
+    final = following is None or following > end or any(onset < b <= following for b in boundaries)
+    if previous_end is None or onset > previous_end or onset in boundaries:
+      previous = ''
+    beat, onbeat = pulse(measure, fraction(note['onset']))
+    text = syllable(end - onset, beat, onbeat, final, previous)
+    values = [{'kind': 'syllabic', 'text': 'single', 'attributes': {}}, {'kind': 'text', 'text': text, 'attributes': {}}]
+    verse = {'number': '1', 'syllables': values}
+    if chain:
+      values.append({'kind': 'extend', 'text': '', 'attributes': {'type': 'start'}})
+      verse['extend_to'] = rational(end)
+      for position, continuation in enumerate(chain):
+        continuation['lyrics'] = [{'number': '1', 'syllables': [{'kind': 'extend', 'text': '', 'attributes': {'type': 'stop' if position == len(chain) - 1 else 'continue'}}], 'extend_to': rational(end)}]
+    note['lyrics'] = [verse]
+    note['lyric'] = text
+    note['lyric_notation'] = {'text': text, 'syllabic': 'single', 'extend': 'start' if chain else ''}
+    previous, previous_end = text, end