  We introduce the notion of multi-pattern, a combinatorial abstraction of
polyphonic musical phrases. The interest of this approach to encode musical
phrases lies in the fact that it becomes possible to compose multi-patterns in
order to produce new ones. This dives the set of musical phrases into an
algebraic framework since the set of multi-patterns has the structure of an
operad. Operads are algebraic structures offering a formalization of the notion
of operators and their compositions. Seeing musical phrases as operators allows
us to perform computations on phrases and admits applications in generative
music. Indeed, given a set of short patterns, we propose various algorithms to
randomly generate a new and longer phrase inspired by the inputted patterns.
