Here's something interesting if you use MP3 files for backing...

I got the Creative Labs Sound Blaster Audigy2 ZS Laptop PCMCIA soundcard for my Acer Ferrari notebook computer. It has a nice clean sound and good specs, but what really was neat was that it came with several software programs including "Media Organizer". This media database program can playback MIDI, WAV and MP3 files, but it can also analyze the volume of your MP3 files and play them all back at relatively the same volume (handy!), and it has a real time control for adjusting file playback speed - so you can adjust the song tempo smoothly, live, without affecting the pitch, just like you can with a MIDI file!

I went from using Yamaha's defunct XG softsynth on my laptop to using MP3 files that I created by recording my MIDI files playing on my Yamaha 9000 Pro keyboard. The files sound very good and work great as backing when I play a client-supplied piano (I still use the 9000 Pro live when no piano is available). This tactic was meant as a stop-gap measure until I find the right GM softsynth, like Bandstand or similar, to play my MIDI files live and work with OMB as an interactive arranger on my laptop. Once I decide on an acoustic piano sample program for live use (NI's Akoustic Piano possibly) and get my CME UF8 controller (I'm selling my loaded Motif ES 8 later this month) then I plan to migrate from the 9000 Pro to using my "Esh2006" system fulltime.