Comping

generator/acoustic.py

@@ -6,6 +6,7 @@ import itertools
 
 import generator.accompaniment
 import generator.model
+import generator.score
 
 @dataclasses.dataclass
 class HarmonySpan:
@@ -107,3 +108,41 @@ def combine(document: dict) -> None:
       a = fragments[start][-1] if start in fragments else originals[start]
       b = fragments[end][0] if end in fragments else originals[end]
       a['tie_to'], b['tie_from'] = b['id'], a['id']
+
+def validate_comping(document: dict) -> None:
+  """Check complete sounding events, not barline or notation fragments."""
+  tones, starts, cursor = {}, {}, fractions.Fraction()
+  for measure in document['staves'][0]['measures']:
+    for note in generator.score.measure_notes(measure):
+      for pitch in note['pitches']:
+        tones[pitch['id']] = pitch
+        starts[pitch['id']] = cursor + generator.model.fraction(note['onset'])
+    cursor += generator.model.fraction(measure['duration'])
+  groups = {}
+  for identifier, pitch in tones.items():
+    if pitch.get('tie_from') in tones:
+      continue
+    start, tail = starts[identifier], pitch
+    seen = {identifier}
+    while tail.get('tie_to') in tones:
+      target = tail['tie_to']
+      if target in seen:
+        raise ValueError('cyclic acoustic sustain')
+      seen.add(target)
+      tail = tones[target]
+    end = starts[tail['id']] + generator.model.fraction(tail['duration'])
+    string = pitch.get('tablature', {}).get('string')
+    if string is None:
+      raise ValueError('acoustic comping requires placed notes')
+    groups.setdefault((start, end), set()).add('bass' if string >= 5 else 'upper')
+  events = []
+  for (start, end), lanes in groups.items():
+    if len(lanes) == 2:
+      if end - start <= 1:
+        raise ValueError('combined acoustic sustain must exceed one beat')
+    elif end - start not in (fractions.Fraction(1, 2), 1):
+      raise ValueError('separate acoustic comping requires quarter/eighth notes')
+    events.append((start, end))
+  events.sort()
+  if any(a[1] > b[0] for a, b in zip(events, events[1:])):
+    raise ValueError('acoustic bass and upper must release together or remain separate')