A musical structure is either an event, a cycle of structures, or a polymetry of structures.    From Wordnik.com.  [Patterns in Haskell « Alex McLean] Reference

A cycle allows us to sequence structures one after another, and a polymetry allows us to represent several structures occuring over the same period of time.    From Wordnik.com.  [Patterns in Haskell « Alex McLean] Reference