MUSICA (MUSical Interative Collaborative Agent) is part of the DARPA Communicating with Computers program and focuses on interaction and communication between humans and machines in musical domains. MUSICA features two uses cases: Composition by Conversation (CbC) and Trading Fours.

Composition by Conversation is a scenario where a human and computer collaboratively compose and edit music through natural language. This task involves modeling natural language for musical concepts, developing computational models of music that facilitate integration with natural language processing algorithms, querying a score for musical features based on partial specifications of concepts, and generating new music based on user descriptions.

Trading Fours focuses on modeling the interaction between jazz musicians, where participants alternate improvising 4-measure-long passages. Communication takes place through the creation and adoption of musical motifs between the instrumentalists. Problems for the computer in this domain involve pattern detection (locating musical motifs), pattern-based generation, and making stylistically correct decisions.