Transpose

generator/guitar.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+from fractions import Fraction
+from typing import NamedTuple
+
+STANDARD_TUNING = ((6, 40), (5, 45), (4, 50), (3, 55), (2, 59), (1, 64))
+MIN_FRET = 0
+MAX_FRET = 15
+MAX_FRET_SPAN = 4
+WRITTEN_GUITAR_OCTAVE_OFFSET = 12
+
+class TabPosition(NamedTuple):
+  string_number: int
+  fret: int
+  midi: int
+
+def within_fret_span(positions) -> bool:
+  fretted = [position.fret for position in positions if position.fret > 0]
+  return not fretted or max(fretted) - min(fretted) <= MAX_FRET_SPAN
+
+def positions_for_pitch(midi: Fraction) -> tuple[TabPosition, ...]:
+  if midi.denominator != 1:
+    return ()
+  return tuple(TabPosition(string, int(midi - open_midi), int(midi)) for string, open_midi in STANDARD_TUNING if MIN_FRET <= midi - open_midi <= MAX_FRET)