I expect this is obvious to everyone, but I realised it only recently and it's remotely possible that someone else might find it useful. Being an idle fellow, I was looking for a fast way to produce nicely-harmonised passages for various combinations of JABB instruments (I mostly use SONAR 5). It occurred to me that Band in a Box will correctly harmonise the melody line according to the entered progression, and there's a vast list of styles and voicings including the standard jazz structures like drop 2. After recording the top line of the ensemble passage as a melody line and auditioning the different harmonised lines until I get what I want, I then save the piece as a midi 1 file. This makes a separate midi track for each of the instruments in the ensemble, which can then be imported into SONAR and assigned to the appropriate JABB voices. Of course it's still necessary to work on the controllers to get the right articulation, but I'm impressed at how quickly it's possible to create quite convincing ensemble passages from scratch.