This invention relates to an automatic rhythm-pattern accompaniment equipment for an electronic musical instrument, capable of inserting so called fill-in rhythm for a short period when a rhythm-pattern is shifted from one pattern to another while the instrument is being played. 
A player often needs to change an accompaniment rhythm-pattern--a basic rhythm-pattern or a variation rhythm-pattern--directly into another accompaniment rhythm-pattern.  In the automatic rhythm-pattern accompaniment equipment of conventional electronic musical instruments, it is often the case that an unusual acoustical change occurs when a rhythm is changed into another rhythm having no relevance to the previous one.  For a continuous variation of playing rhythm-pattern, it has been practiced to insert a switch-over rhythm for a short period on playing drums which is called "fill-in". 
An electronic musical instrument has been known that can automatically generate accompaniment rhythm-pattern and has capacity to insert a rhythm when operated manually.  In the conventional electronic musical instrument of this kind, the player must close the switch at the moment the fill-in rhythm is inserted in order to superpose the fill-in sound on the rhythm sound being played, and he must open the switch at the exact moment the rhythm-pattern is changed.  Therefore, it was difficult to adjust the time accurately.  Since the output of the clock pulse oscillator for the accompaniment rhythm-pattern is asynchronous to the output of the pulse generator for the fill-in rhythm, the new fill-in rhythm pattern does not match well to said existing rhythm-pattern, so that is was difficult to eliminate unusual acoustic effect.