justforfun000 what you say is right.
Solton solo sounds are using 1 2 3 or 4 GM sound in 1 2 3 or 4 midi chanels simultanously. All demo you heard are probably the SD-1 played live with the aranger section, and this section are played with midi instrument (1 chanel).Just solo sounds uses multi chanels.
You can do a midifile with the same sound you heard in the DEMO.
and when I play a midifile from internet in my SD-1, it play great! more all than i heard.

SD-1 "premier" sound are very loud. for example piano sound or strings sound are very punchy. you can use only 1 of them in a midifile sequenced in the SD1 (you can change it of course).

but it's not realy a problem because the SD-1 is the best keyboard...

I think in midi 1 chanel can oly play one sound at time.

(i m french and i don't learn english. I can write little english because I read you. so than that this there those.... shit ))