CatOracle responds to the need to join high-level control of audio timbre with the organization of musical form in time. It is inspired by two powerful existing tools: CataRT for corpus-based concatenative synthesis based on the MuBu for Max library, and PyOracle for computer improvisation, combining for the first time audio descriptor analysis and learning and generation of musical structures. Harnessing a user-defined list of audio features, live or prerecorded audio is analyzed to construct an "Audio Oracle" as a basis for improvisation. CatOracle also extends features of classic concatenative synthesis to include live interactive audio mosaicking and score-based transcription using the Bach library for Max. The project suggests applications not only to live performance of written and improvised electroacoustic music, but also computer-assisted composition and musical analysis.