Scott, I think you will need Performer as well since any built-in playback was removed from Composer by then to accommodate the growing size of each program. To playback a Composer file you had to open it in Performer. Will you confirm that? I think it was only the 1984 versions that had a built in sequencer software, if at all. Performer came out in 85, but I don't remember when exactly they separated them completely.

I have copies of both somewhere, but I do not recall where they are at the moment. Also MOTU used a rather rigorous copy protection scheme, but I think I was able to make images using Copy II Plus. Keep looking on your own, since it'll take me some time to dig up mine.