I think you were clear enough Bernie. You need a midi-merger (about 50-100 $$) to connect two midi sources (like a laptop and a keyboard) to one midi in (like a SD2). Then you send Bank select and program change messages from your sources (of course they must have this function) to choose whatever sound you wish. But if this doesn´t answer your question, then I have misunderstood you completely and I am sorry for that.