I'll try to answer as much as I know:
1)
To play a sound effect, use.
(send gTheSoundFX: prevSignal(0) stop() number(20) loop(1) play())
where the
20 or whatever i s the sound number to play.
2) You could download a midi creation program. I recommend Anvil Studio, (
www.AnvilStudio.com ). There create your midis and midi-sound-fx. Then use Soundbox to import your midi, and from the Edit > Channel Properties .. and tick all the
Play Flags in the played channels. Then Save As to SCI sound format. Import it into your game, and you should be able to use it.
For some reason all the sound cards don't play those home made sounds. But you could try one of the other sound drivers (The attachment) . Just edit the soundDrv = ... line in resource.cfg file to find the one that works for you.
For me, as I have SB Live!, gm.drv and mpumidi.drv work. They should work with the newer on-board sound cards too.
The attachment also includes one sci sound made from a midi, use it to check if it works.
-Eigen