Repetition is important in music, where sounds or sequences are often repeated. It may be called restatement, such as the restatement of a theme. While it plays a role in all music, with noise and musical tones lying along a spectrum from irregular to periodic sounds,( Moravcsik, 114 ) ( Rajagopal ) it is especially prominent in specific styles. A literal repetition of a musical passage is often indicated by the use of a repeat sign, or the instructions da capo or dal segno.

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Repetition is a part and parcel of symmetry—and of establishing motifs and hooks. You find a melodic or rhythmic figure that you like, and you repeat it throughout the course of the melody or song. This sort of repetition…helps to unify your melody; it’s the melodic equivalent of a steady drumbeat, and serves as an identifying factor for listeners. However, too much of a good thing can get annoying. If you repeat your figure too often, it will start to bore the listener.
— (Miller, 106)

Memory affects the music-listening experience so profoundly that it would be not be hyperbole to say that without memory there would be no music.

As scores of theorists and philosophers have noted…music is based on repetition. Music works because we remember the tones we have just heard and are relating them to the ones that are just now being played. Those groups of tones—phrases—might come up later in the piece in a variation or transposition that tickles our memory system at the same time as it activates our emotional centers…Repetition, when done skillfully by a master composer, is emotionally satisfying to our brains, and makes the listening experience as pleasurable as it is.
— ( Levitin, 162-163 )