I want to be able to hear guitar pro coming from my computer via headphone jack AND my Line 6 amp so that I can play and not bother anyone. This would be a great help, does anyone know what kind of adapter I would need?

I'm guessing your line 6 has a line in for mp3 players or something, right? Just attach a 1/8"-18" male-male cable from your headphone output on the computer to the mp3 line in on the amp.
Telecaster - SG - Jaguar
Princeton Reverb, Extra Reverb
P-Bass - Mustang Bass
Apogee Duet 2 - Ableton Suite
You could run both into a small mixing desk and take a headphone output.
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