The MIDI synth in your yamaha keyboard has some really good sounds in it. Not only that, use of the hardware MIDI synth inside the keyboard allows near zero latency at all times, something unobtainable when using software MIDI synths. This is likely of importance only if you are recording your keyboard playing in realtime. The luscious sounds inside that keyboard are reason enough, though, you have them and might as well make use of them. Connecting the MIDI to the computer and selecting the proper Input and Output to send what BB plays as MIDI to that keyboard's internal synth is a different world of sound from using internal software synthesizers for MIDI.

Looking at the Yamaha DGX640's .pdf manual, available on the yamaha instruments website, I see that all you need is a single USB cable to attach this keyboard to the computer. You must install the USB drivers that are provided on the CD that shipped with the keyboard. If that's lost, it likely can be downloaded from the yamaha support site.

There are about 500 different MIDI voices in your piano, and 11 MIDI percussion banks. You will likely want to have a Patchmap to drop into the BB folder and select inside BB so that you can access all those by name using the + button to the right of the standard GM patches already listed in the dropdown. Check the PGMusic Support Pages, under Patchmaps to see if someone has already written and posted one to download. If you don't see one for your 640, don't despair, there's a wizard inside BB that can convert a Cakewalk .ins file to a bb patchmap with a single mouse button push. Websearch engine should bring up a cakewalk .ins file for this popular instrument.

Other than that, there's no hard pat reason to have to hook it up to the computer if all your needs are just to be able to play piano along with Band in a Box.

Have Fun,

--Mac