diff --git a/CHANGELOG.md b/CHANGELOG.md
index e7c3a88..63f5479 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 All notable changes to PyTheory are documented here.
 
+## 0.41.3
+
+- **Fix** — `to_abc()` now skips parts with only drum tones or rests (no pitched
+  notes), fixing "pitch is undefined" errors in abcjs. Chords are correctly
+  recognized as pitched content.
+
 ## 0.41.2
 
 - **Auto bass clef** — `to_abc()` detects low-register parts (808, bass, timpani)
diff --git a/pyproject.toml b/pyproject.toml
index a9308ba..a5e7daa 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "pytheory"
-version = "0.41.2"
+version = "0.41.3"
 description = "Music Theory for Humans"
 readme = "README.md"
 license = "MIT"
diff --git a/pytheory/__init__.py b/pytheory/__init__.py
index 43c4b2c..9a4ea48 100644
--- a/pytheory/__init__.py
+++ b/pytheory/__init__.py
@@ -1,6 +1,6 @@
 """PyTheory: Music Theory for Humans."""
 
-__version__ = "0.41.2"
+__version__ = "0.41.3"
 
 from .tones import Tone, Interval
 from .systems import System, SYSTEMS, TET
diff --git a/pytheory/rhythm.py b/pytheory/rhythm.py
index d2d9744..981fe21 100644
--- a/pytheory/rhythm.py
+++ b/pytheory/rhythm.py
@@ -4396,15 +4396,25 @@ class Score:
             f"L:1/{default_unit}",
         ]
 
-        # Collect voices: default notes first, then named parts (skip drums)
+        # Collect voices: default notes first, then named parts
+        # Skip drum parts and parts with no pitched notes
         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))
+            if not part.notes:
+                continue
+            # Skip parts that have no pitched tones (only drum tones / rests)
+            has_pitched = any(
+                n.tone is not None
+                and (hasattr(n.tone, "name") or hasattr(n.tone, "tones"))
+                for n in part.notes
+            )
+            if not has_pitched:
+                continue
+            voices.append((name, part.notes))
 
         multi = len(voices) > 1
 
diff --git a/uv.lock b/uv.lock
index 887f1d7..9f89de3 100644
--- a/uv.lock
+++ b/uv.lock
@@ -690,7 +690,7 @@ wheels = [
 
 [[package]]
 name = "pytheory"
-version = "0.41.2"
+version = "0.41.3"
 source = { editable = "." }
 dependencies = [
     { name = "rich" },