By no means am I a recording expert, but to sum up what Emil tried to tell you is when you record on different tracks, if you are using the same channel number....even though you are using different instrument sounds on each track, it will send the sound of the channel selected. So if by default your selection is channel 1 lets say, then you put piano on track 1 and bass on track2, but channel 1 is selected for both tracks, and you are having your sequencer software play off of channel 1 only, then both tracks will play the piano sound. Finally, each track has to have its own channel...I hope I helped you rather than confused you!

Good luck