I've been trying out the rhythm mode for OPL2 and OPL3 (the mode where the operators of the last three channels are used to generate percussion sounds), but I can't seem to work it out. The only drum I can get to make a sound at all is the hi-hat (bit 1 in register 0xBD). Yesterday I got to a point where I was just filling the OPL registers with random data (except the gate bits were unset) and playing through the drum sounds, but still I only get the hi-hat to work. Thinking it must have been a bug in DOSBox, I tried it with a real OPL (on a toshiba libretto) with the same results.

There is very little documentation on this mode; was it ever used by anyone at all? Is there any source code I can read on the subject, or any easily parseable register dumps of a typical rhythm mode setup? I'm sorry if this isn't the most appropriate sub-forum, but this is the only place I can think of where I can ask a question like this and get a knowledgable answer. I used the rhythm mode on OPLL chips before, which had its hassles, but was a no-brainer compared to figuring out how to do it on the OPL2 or OPL3.