Descriptive of a control used to operate a pneumatic musical instrument. One short perforation locks the mechanism in the "on" position, in which position it remains until another perforation releases it to the "off" position. In this way an effect (a pipe register, for example) can be "on" for a long period of time without having to use an extended or chain perforation, which would weaken the paper. See general cancel.
MBSI
Musical Box Society International