This stuff has been around for a long time, but it doesn’t seem to have been updated for quite a long time now, which is a bit of a shame really.
If you check out their site there is lots of software there. From sequencers to MIDI apps and even a 4-track. However, the four track takes 4 .wav files and puts them side by side with some control of the volumes of each file. Still, worth a look.