maybe fixed?

music21/chord/__init__.py

@@ -443,8 +443,6 @@ def volume(self) -> 'music21.volume.Volume':  # do NOT change to volume.Volume,
 
         * Changed in v8: setting volume to a list of volumes is no longer supported.
           See :meth:`~music21.chord.ChordBase.setVolumes` instead
-        * Improved in v9: if hasComponentVolumes is True, then the velocity object
-          returned here will be regenerated with each call, and updates live.
 
         OMIT_FROM_DOCS
 
@@ -473,6 +471,7 @@ def volume(self) -> 'music21.volume.Volume':  # do NOT change to volume.Volume,
         if velocities:  # avoid division by zero error
             out_volume.velocity = int(round(sum(velocities) / len(velocities)))
 
+        self._volume = out_volume
         return out_volume
 
 
@@ -582,9 +581,9 @@ def setVolumes(self, volumes: Sequence['music21.volume.Volume'|int|float]):
                 v = v_entry
             else:  # create a new Volume
                 if v_entry < 1:  # assume a scalar
-                    v = volume.Volume(velocityScalar=v_entry)
+                    v = volume.Volume(velocityScalar=float(v_entry))
                 else:  # assume velocity
-                    v = volume.Volume(velocity=v_entry)
+                    v = volume.Volume(velocity=int(v_entry))
             v.client = self
             c._setVolume(v, setClient=False)
 

music21/volume.py

@@ -406,13 +406,17 @@ def velocityScalar(self, value: int|float|None):
         if not common.isNum(value):
             raise VolumeException('value provided for velocityScalar must be a number, '
                                   + f'not {value}')
+
+        scalar: float
         if value < 0:
-            scalar = 0
+            scalar = 0.0
         elif value > 1:
-            scalar = 1
+            scalar = 1.0
         else:
-            scalar = value
-        self._velocityScalar = float(scalar)
+            if t.TYPE_CHECKING:
+                assert value is not None
+            scalar = float(value)
+        self._velocityScalar = scalar
 
 
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