Do you have any basic c# coding skills?
If yes, than using http://code.google.com/p/midi-dot-net/
you can write a small midi synthesizer, for example something like a virtual instrument, this library is able to play the sounds of the windows midi set, for example you could make like 20 buttons to make a small piano.
As far as I know, the Bass Library can only play midi files, not create or modify.
I think there is software too to record what your midi keyboard outputs in midi format on the pc, but this Forum is the Forum of the Bass Library so its not related much to what you want.