Midi Newbie Lost Options

[eternaluxe]

Hi gang. I'm totally new to this MIDI game and need some help to get started.
I just got a Yamaha PSR-172 keyboard (Very basic, but it has midi in/out)
I'm using a PBG3 (pre-usb) with a mini MacMan 1 in/1 out.
It's running OS 9.2.
I've downloaded cellsynth and am trying to get something out of it.
I've tried setting everything up, but am not sure how to do it properly. Could someone give me a step by step that will take me to the point where when I press a key on the Yamaha, I get sound from the mac? It doesn't have to be with the cellsynth program, it can be with a different one, but the program has to be free to try out. I just need to have that little push in the right direction.
Thanks in advance,
-Patrick

[eternaluxe]

Here's the setup: PowerBook G3 pre-usb, OS 9.2, miniMacman in the modem port. Midi in to Midi out, Midi out to Midi in, connected to a Yamaha PSR-172.
As far as OMS being set up correctly, I do believe it is. I've never set it up before, so I can't really be sure. When I start up an audio prog (proTools free or the otheron I mentioned earlier, CellSynth) the minMacMan power led lights red, and the MIDI in light soft flickers amber. When I press a key on the Yamaha, the MIDI in led goes to full for a moment before settling back to the flicker. No MIDI out led activity whatsoever. Does this make sense?
Any how, from this info I believe that OMS is set up properly, I just don't know how to set up the apps test it out. (play a sound when I press a key). I'd be happy to provide more info if necessary. Also, if there is an os9 app that you are familiar with, I'd be willing to try setting it up instead. I just want to get it working with anything so That I can be sure that it works at all.