The characteristic of something to move thru a certain number of cycles which exhibit repetition, in a certain period of time or space.
When applied to a regularly-repeating vibration, this number is called the vibration's frequency.
Many aspects of music exhibit periodicity:
Other art forms may also exhibit periodicity, for example, Islamic tile art, architecture, Native American rugs, possibly cinema...but none seems to place as much emphasis on it as music. This is probably due to the importance of time as a dimension of musical perception.
Periodicity also plays a part in defining the finity of an intonational system. See periodicity-block.
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