Transpose

generator/transposition.py

@@ -80,15 +80,20 @@ def shift_key(key: dict, steps: int, semitones: int) -> dict:
       result['custom'] = True
   return result
 
-def transpose_document(document: dict, target_key_name: str) -> dict:
+def transposition_interval(document: dict, target_key_name: str) -> tuple[int, int]:
+  metadata = document['metadata']
+  origin = metadata['key'].get('tonic') or metadata.get('transpose_origin')
+  if origin is None:
+    raise ValueError('keyless practice requires a vamp:tonic score property')
+  return interval_between(origin, parse_pitch_name(target_key_name))
+
+def transpose_document(document: dict, target_key_name: str, *, octave_shift: int = 0) -> dict:
+  if type(octave_shift) is not int:
+    raise ValueError('octave adjustment must be an integer')
+  steps, semitones = transposition_interval(document, target_key_name)
   output = copy.deepcopy(document)
   metadata = output['metadata']
   key = metadata['key']
-  origin = key.get('tonic') or metadata.get('transpose_origin')
-  if origin is None:
-    raise ValueError('keyless melody practice requires a vamp:tonic score property')
-  target = parse_pitch_name(target_key_name)
-  steps, semitones = interval_between(origin, target)
   metadata['key'] = shift_key(key, steps, semitones)
   metadata['key_signature'] = key_label(metadata['key'])
   metadata['variant_tonic'] = target_key_name
@@ -106,7 +111,10 @@ def transpose_document(document: dict, target_key_name: str) -> dict:
         h['symbol'] = harmony.symbol(h)
       for voice in measure['voices']:
         for note in voice['notes']:
-          note['pitches'] = [shift_pitch(p, steps, semitones) for p in note.get('pitches', [])]
+          try:
+            note['pitches'] = [shift_pitch(p, steps + 7 * octave_shift, semitones + 12 * octave_shift) for p in note.get('pitches', [])]
+          except ValueError as error:
+            raise ValueError(f'measure {measure.get("number", measure["id"])}, voice {voice["id"]}, event {note["id"]}: {error}') from error
   return output
 
 def concert_document(document: dict) -> dict: