Hi Donald,
Are these tracks in a Midi format?
I can tell you this, the Silent Brass rig (I have one and have used it for all sorts of applications) does have that headphone output. You can connect the silent brass's headphone out to the LINE IN on your computer's sound card. You'd then need to use some sort of recording/mixing/editing program to record your work. That same program should be able to import the tracks your buddy sent you so that you can listen to those tracks while recording along with them.
This is fine for pre-production work... but you know as well as I do that the sound you get from the silent brass is something like a cup mute inside a box. It's not the best sound, but it gets the job done.
If you wanted to do the job without the use of the silent brass, then you're going to need a mic, mic cable, XLR to 1/4" adapter and some sort of pre-amp with 1/4" input ( I use an old Pioneer Tape Deck, beleive it or not) This will allow for more natural sound quality and get you closer to a home-brewed recording.
Hope this helps... feel free to follow up with other questions.
Caleb Denison
Caleb Denison
Home Theater Guru
Aperionaudio.com