diff --git a/pytheory/rhythm.py b/pytheory/rhythm.py
index 1d0abef..e42c585 100644
--- a/pytheory/rhythm.py
+++ b/pytheory/rhythm.py
@@ -4369,6 +4369,157 @@ class Score:
f"{part_info} {self.measures:.1f} measures>"
)
+ # ── ABC notation export ────────────────────────────────────────────
+
+ def to_abc(self, *, title="Untitled", key="C", html=False):
+ """Export the score as ABC notation.
+
+ Args:
+ title: Tune title for the ``T:`` field.
+ key: Key signature (e.g. ``"C"``, ``"Gm"``, ``"D"``) for the
+ ``K:`` field.
+ html: If *True*, wrap the ABC string in a self-contained HTML
+ page that renders sheet music via abcjs.
+
+ Returns:
+ An ABC notation string, or a full HTML document string when
+ *html* is True.
+ """
+ ts = self.time_signature
+ default_unit = 8 # L:1/8
+
+ lines = [
+ "X:1",
+ f"T:{title}",
+ f"M:{ts.beats}/{ts.unit}",
+ f"Q:1/4={self.bpm}",
+ f"L:1/{default_unit}",
+ ]
+
+ # Collect voices: default notes first, then named parts (skip drums)
+ voices: list[tuple[str, list]] = []
+ if self.notes:
+ voices.append(("default", self.notes))
+ for name, part in self.parts.items():
+ if part.is_drums:
+ continue
+ if part.notes:
+ voices.append((name, part.notes))
+
+ multi = len(voices) > 1
+
+ if multi:
+ for i, (vname, _) in enumerate(voices, 1):
+ lines.append(f"V:{i} name=\"{vname}\"")
+ lines.append(f"K:{key}")
+ for i, (_, notes) in enumerate(voices, 1):
+ lines.append(f"V:{i}")
+ lines.append(self._notes_to_abc(notes, default_unit, ts))
+ else:
+ lines.append(f"K:{key}")
+ if voices:
+ lines.append(self._notes_to_abc(voices[0][1], default_unit, ts))
+
+ abc = "\n".join(lines) + "\n"
+
+ if not html:
+ return abc
+
+ return (
+ "\n\n"
+ "" + title + "\n"
+ "\n"
+ "\n\n\n\n"
+ )
+
+ @staticmethod
+ def _tone_to_abc(tone, default_unit):
+ """Convert a single Tone to an ABC note string."""
+ if tone is None:
+ return "z"
+
+ name = tone.name # e.g. "C", "C#", "Bb"
+ octave = tone.octave if tone.octave is not None else 4
+
+ # ABC accidentals: ^ = sharp, _ = flat, ^^ = double sharp, __ = double flat
+ letter = name[0].upper()
+ acc = name[1:] if len(name) > 1 else ""
+ abc_acc = acc.replace("##", "^^").replace("#", "^").replace("bb", "__").replace("b", "_")
+
+ # ABC octave: C-B = octave 4, c-b = octave 5,
+ # c' = 6, c'' = 7, C, = 3, C,, = 2
+ if octave >= 5:
+ note_char = letter.lower()
+ ticks = octave - 5
+ oct_str = "'" * ticks
+ else:
+ note_char = letter.upper()
+ commas = 4 - octave
+ oct_str = "," * commas
+
+ return f"{abc_acc}{note_char}{oct_str}"
+
+ def _notes_to_abc(self, notes, default_unit, ts):
+ """Convert a list of Note objects to an ABC body string."""
+ beats_per_measure = ts.beats_per_measure
+ parts = []
+ beat_in_measure = 0.0
+
+ for note in notes:
+ beats = note.duration.value
+
+ # ABC length multiplier relative to L:1/default_unit
+ # L:1/8 means 1 unit = 0.5 beats (an eighth note)
+ unit_beats = 4.0 / default_unit # beats per L unit
+ multiplier = beats / unit_beats
+
+ if note.tone is None:
+ abc_note = "z"
+ elif hasattr(note.tone, "tones"):
+ # Chord: [CEG]
+ chord_notes = [
+ self._tone_to_abc(t, default_unit)
+ for t in note.tone.tones
+ ]
+ abc_note = "[" + "".join(chord_notes) + "]"
+ else:
+ abc_note = self._tone_to_abc(note.tone, default_unit)
+
+ # Format duration multiplier
+ if multiplier == 1:
+ dur_str = ""
+ elif multiplier == int(multiplier):
+ dur_str = str(int(multiplier))
+ elif multiplier == 0.5:
+ dur_str = "/2"
+ elif multiplier == 0.25:
+ dur_str = "/4"
+ elif multiplier == 1.5:
+ dur_str = "3/2"
+ else:
+ # General fraction
+ from fractions import Fraction
+ frac = Fraction(multiplier).limit_denominator(16)
+ dur_str = f"{frac.numerator}/{frac.denominator}"
+
+ parts.append(f"{abc_note}{dur_str}")
+
+ beat_in_measure += beats
+ if beat_in_measure >= beats_per_measure - 0.001:
+ parts.append("|")
+ beat_in_measure -= beats_per_measure
+
+ body = " ".join(parts)
+ # Clean up trailing/double barlines
+ body = body.replace("| |", "|").rstrip("| ").rstrip()
+ if not body.endswith("|"):
+ body += " |"
+ return body
+
def save_midi(self, path, velocity=100):
"""Export to Standard MIDI File, measure-aware."""
ticks_per_beat = 480