Length in quarter-note beats of the bar containing a beat.
The meter-map counterpart of beatsPerBar, which answers for one
signature and so cannot be asked about a piece that changes meter.
The bar the beat is in, not the bar its signature nominally has: a change of
meter starts a new bar, so a bar interrupted by one is shorter than its own
signature says. Reading the signature's own length there would put the end of
the bar past where the next one begins, and every span measured in bars from
that point on would be counted against a bar length the music never had.
Length in quarter-note beats of the bar containing a beat.
The meter-map counterpart of beatsPerBar, which answers for one signature and so cannot be asked about a piece that changes meter.
The bar the beat is in, not the bar its signature nominally has: a change of meter starts a new bar, so a bar interrupted by one is shorter than its own signature says. Reading the signature's own length there would put the end of the bar past where the next one begins, and every span measured in bars from that point on would be counted against a bar length the music never had.