Time is administered by the Time_signature_engraver, which usually lives in the Score context. The bookkeeping deals with the following variables
currentBarNumbermeasureLengthmeasurePositionmeasureLength. When that
happens, currentBarNumber is incremented.
timingTiming can be changed by setting any of these variables explicitly.
In the next example, the 4/4 time signature is printed, but
measureLength is set to 5/4. After a while, the measure is
shortened by 1/8, by setting measurePosition to -3/8 at 2/4 in
the measure, so the next bar line will fall at 2/4 + 3/8.
\set Score.measureLength = #(ly:make-moment 5 4)
c1 c4
c1 c4
c4 c4
\set Score.measurePosition = #(ly:make-moment -3 8)
b8 b b
c4 c1
This page is for LilyPond-2.4.5 (stable-branch).