I don't know if you are familiar with the program Reason, but it is a soft synth that has drums, synth modules and many other useful effects etc. If you had this program on your computer you could hook up your keyboard via MIDI and control the sounds that way. You would not be recording any audio from your keyboard, just the information to play the notes. Basically you can use you current keyboard to control a virtually limitless amount of sounds of all different kinds (including bass guitar). My favorite part of MIDI is the fact that once you record the MIDI data you can still change the sounds to your liking. Additionally you can change individual notes and placement of those notes. I just used Reason as an example because that is what I am familiar with. There are plenty of soft synths to choose from.