Span

generator/guitar.py

@@ -32,12 +32,10 @@ def voicing_cost(positions: tuple[generator.fretboard.TabPosition, ...], profile
   classes = {p.midi % 12 for p in positions}
   above = sum(p.midi > max(melody) for p in positions) if melody else 0
   span = compactness(positions)
-  effort = 2 * max(0, max(frets, default=0) - PREFERRED_MAX_FRET)
   if profile == 'electric':
-    effort += max(frets, default=0) + 2 * max(0, len(frets) - 1)
-    effort += 3 * span
+    effort = 2 * max(0, len(frets) - 1) + 3 * span
   else:
-    effort += span
+    effort = 2 * max(0, max(frets, default=0) - PREFERRED_MAX_FRET) + span
   return VoicingCost(max(0, 4 - len(positions)) if profile == 'electric' else 0, int(bool(above)), above, effort, len(set(allowed) - classes))
 
 @functools.lru_cache(maxsize=256)
@@ -61,7 +59,7 @@ def chord_positions(requirements: generator.fretboard.ChordRequirements, prune:
     by_string = {string: options[i] for i, (string, _) in enumerate(generator.fretboard.STANDARD_TUNING)}
     for strings in ELECTRIC_STRINGS:
       for selected in itertools.product(*(by_string[s] for s in strings)):
-        if not generator.fretboard.within_fret_span(selected) or not requirements.covers({p.midi % 12 for p in selected}) or not set(melody) <= {p.midi for p in selected}:
+        if not generator.fretboard.within_fret_span(selected) or not generator.fretboard.has_fret_anchor(selected) or not requirements.covers({p.midi % 12 for p in selected}) or not set(melody) <= {p.midi for p in selected}:
           continue
         if requirements.basses and (selected[0].midi % 12 not in requirements.basses or selected[0].midi != min(p.midi for p in selected)):
           continue
@@ -307,7 +305,7 @@ def advance_positions(notes: list[dict], onset: fractions.Fraction, tones: dict[
   if not result:
     if not fallback and any(n.get('_harmonize') for n in notes):
       return advance_positions(notes, onset, tones, states, preserve_strings, True)
-    raise ValueError(f'event {notes[0]["id"]}, onset {onset}: no guitar placement within frets {generator.fretboard.MIN_FRET}-{generator.fretboard.MAX_FRET} and three-fret span; held/tied strings must remain fixed')
+    raise ValueError(f'event {notes[0]["id"]}, onset {onset}: no guitar placement within frets {generator.fretboard.MIN_FRET}-{generator.fretboard.MAX_FRET} and at most {generator.fretboard.MAX_FRET_SPAN} consecutive fret positions; electric chords need a fret <= {generator.fretboard.MAX_ANCHOR_FRET}; held/tied strings must remain fixed')
   return result
 
 def place_guitar(document: dict) -> None: