Thanks for the response John. Since you have the SD2 is it possible to connect the SD-2 to a computer and keyboard simultaneously. Both my computers have soundcards with midi in and out connections. Audio outs would be going through small mackie mixers connected to sound cards audio connections. Usually use a yamaha s-90 for playback via midi (not usb). Wanted a smaller desktop unit for flexibility between computers and future laptop purchase. Can you provide a quick hook up guide for Sd2--computer--midi keyboard? Presumed the SD-4 would give me more connection options. Thanks again