What is a sequence in music and how does it contribute to the overall structure and development of a musical composition?

In music, a sequence is a pattern of notes or chords that are repeated at different pitch levels. Sequences help create a sense of unity and coherence in a musical composition by providing a recurring motif that can be developed and varied throughout the piece. They contribute to the overall structure by adding variety and interest, as well as helping to build tension and release within the music.