What did you intend to have happen when beatLength is changed? AFAICS,
\time 12/16 sets measureLength to (ly:make-moment 12 16) and beatLength to
(ly:make-moment 1 16). When a user sets beatLength to (ly:make-moment 1
8) it
says to me they want to have an 8 in the denominator of the time
signature,
even though they want the printed value to be 16.
For me, that should be the only reason for using beatLength. I don't
think
beatLength is the appropriate thing to use for changing beaming. That's
what
beatGrouping is for.
If it were up to me, I would not allow users to directly change
beatLength. I
don't think that a disconnect between the \time setting and the beatLength
setting should be allowed. If users want to fake time signatures, they
can --
and the techniques to do this are shown in the manual.
But, as long as we are allowing users to set beatLength to 1/8, when the
measure length is 12/16, aren't we really saying that the measure should
be
6/8 (i.e. 12 16th notes = 6 eighth notes, and the measure should be
divided
into beats by eighth notes)?
What other interpretation is there for beatLength?