Tie long notes across barlines in to_abc() — v0.41.4

Notes longer than one measure are split into tied pieces so abcjs
can render them correctly (e.g. 16-beat choir drone becomes four
tied whole notes).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes to PyTheory are documented here.
 
+## 0.41.4
+
+- **Fix** — `to_abc()` now ties long notes across barlines instead of emitting
+  oversized durations that abcjs can't render (e.g. 16-beat notes become four
+  tied whole notes).
+
 ## 0.41.3
 
 - **Fix** — `to_abc()` now skips parts with only drum tones or rests (no pitched

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "pytheory"
-version = "0.41.3"
+version = "0.41.4"
 description = "Music Theory for Humans"
 readme = "README.md"
 license = "MIT"

pytheory/__init__.py

@@ -1,6 +1,6 @@
 """PyTheory: Music Theory for Humans."""
 
-__version__ = "0.41.3"
+__version__ = "0.41.4"
 
 from .tones import Tone, Interval
 from .systems import System, SYSTEMS, TET

pytheory/rhythm.py

@@ -4499,6 +4499,24 @@ class Score:
 
         return f"{abc_acc}{note_char}{oct_str}"
 
+    @staticmethod
+    def _format_dur(multiplier):
+        """Format an ABC duration multiplier string."""
+        if abs(multiplier - 1) < 0.001:
+            return ""
+        elif abs(multiplier - int(multiplier)) < 0.001:
+            return str(int(multiplier))
+        elif abs(multiplier - 0.5) < 0.001:
+            return "/2"
+        elif abs(multiplier - 0.25) < 0.001:
+            return "/4"
+        elif abs(multiplier - 1.5) < 0.001:
+            return "3/2"
+        else:
+            from fractions import Fraction
+            frac = Fraction(multiplier).limit_denominator(16)
+            return f"{frac.numerator}/{frac.denominator}"
+
     def _notes_to_abc(self, notes, default_unit, ts,
                       bars_per_line=4):
         """Convert a list of Note objects to an ABC body string."""
@@ -4508,17 +4526,12 @@ class Score:
         measure_count = 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)
+            total_beats = note.duration.value
             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
@@ -4527,33 +4540,32 @@ class Score:
             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}"
+            # Split notes longer than one measure into tied pieces
+            remaining = total_beats
+            first_chunk = True
+            while remaining > 0.001:
+                # How much room left in this measure?
+                room = beats_per_measure - beat_in_measure
+                chunk = min(remaining, room) if remaining > room + 0.001 else remaining
+                needs_tie = remaining - chunk > 0.001
 
-            tokens.append(f"{abc_note}{dur_str}")
+                multiplier = chunk / unit_beats
+                dur_str = self._format_dur(multiplier)
 
-            beat_in_measure += beats
-            if beat_in_measure >= beats_per_measure - 0.001:
-                measure_count += 1
-                if measure_count % bars_per_line == 0:
-                    tokens.append("|\n")
-                else:
-                    tokens.append("|")
-                beat_in_measure -= beats_per_measure
+                tie_str = "-" if needs_tie and abc_note != "z" else ""
+                tokens.append(f"{abc_note}{dur_str}{tie_str}")
+
+                remaining -= chunk
+                beat_in_measure += chunk
+                first_chunk = False
+
+                if beat_in_measure >= beats_per_measure - 0.001:
+                    measure_count += 1
+                    if measure_count % bars_per_line == 0:
+                        tokens.append("|\n")
+                    else:
+                        tokens.append("|")
+                    beat_in_measure -= beats_per_measure
 
         body = " ".join(tokens)
         # Clean up trailing/double barlines

uv.lock

@@ -690,7 +690,7 @@ wheels = [
 
 [[package]]
 name = "pytheory"
-version = "0.41.3"
+version = "0.41.4"
 source = { editable = "." }
 dependencies = [
     { name = "rich" },