Iterate expr. For each measure in expr, multiply contents of measure by n.
Extends containertools.contents_multiply( ) with meter-handling.
Example:
t = RigidMeasure((3, 8), construct.scale(3)) measuretools.spin(t, 3)
time 9/8 c‘8 d‘8 e‘8 c‘8 d‘8 e‘8 c‘8 d‘8 e‘8