[mscuthbert]

TimeSignature.barDuration now is a FrozenDuration (same as one of the underlying MeterSequences). It's necessary since unfreezing that duration on every read made barDuration 30x slower than v10 (0.04 to 1.2 microseconds)

Note that all this prevents this bug that was possible in v10 (since v1 even):

>>> ts = meter.TimeSignature('2/4')
>>> n = note.Note(duration=ts.barDuration)
>>> n.duration.dots = 2
>>> ts.barDuration
<music21.duration.Duration 3.5>

So to do that now do:

>>> ts = meter.TimeSignature('2/4')
>>> n = note.Note(duration=ts.barDuration.unfreeze())
>>> n.duration.dots = 2
>>> ts.barDuration
<music21.duration.FrozenDuration 2.0>

BarDuration is back to 0.08 microseconds, and changing it raises.

Fix romanText which would've broken without this.

Add the meter section to migratingToV11.

AI-assisted (Claude)

[coveralls]

Coverage is 93.761% — meter-frozen-bar-duration into meter-speed-2026. No base build found for meter-speed-2026.