My friend and I play together (two acoustic guitars). Occasionally we play out.
We want to add bass and drums (without adding any people) to our act. We've seen fancy systems (like the one Ron Crites has) that enable even a single performer to be a one man band (all live, with no recorded tracks), but to start off we're OK with just programming digital bass and drum tracks to play to.
My friend has a Bose L1 Compact System (single bass model) and a nice acoustic amp, so that's our point of departure. What's a relatively cheap, fast way to do what we want to do?
I have several software programs that allow me to accomplish this but don't know if this is what you are looking for. However, if you did go my route you can always record and produce your own CD's etc... Thee major things I have:
1. A computer operated DAW (I use cubase) and can be found free bundled
2. Trilian spectrasonics' bass module
3. Groove Agent a drum module made by steinberg (they also make cubase)
Simply open up the DAW then open up the midi drum track and then step record your drum map by individually recording hits for each drum, cymbal etc... then make the output for that track Groove Agent. Do the same for the bass (I usually play the bass part on my midi keyboard) and set the output for the bass track to Trilian.
Then if you want you can controll the velocity of the individual hits to make the performance sound a bit more realisitic. Then mix down to an mp3.