The following technical report is available from http://aib.informatik.rwth-aachen.de: coJIVE: A System to Support Collaborative Jazz Improvisation Jan Buchholz, Eric Lee, Jonathan Klein, and Jan Borchers AIB 2007-04 Jazz improvisation is a complex and demanding art of on-the-fly composition and performance. We present coJIVE, a system that allows musically inexperienced people to improvise to jazz by substituting for musical knowledge and experience. Using well-established musical theory, it aids users in creating a harmonic performance, and also helps coordinate a collaborative session amongst the participants. Remarks from users during evaluation showed an overall positive response to the support provided by the system.