You can connect a bass and mix your bass playing with the track you are playing back.
Connecting a bass
1.Connect a bass to the BASS IN jack.
2.Adjust the bass volume with the INPUT dial.
Practicing with tracks as they play
If you play bass while a track is playing back, you can hear the combined signals of the bass and the track output through the 
/LINE OUT jack.
Use the MIX BALANCE keys to adjust the balance between the track being played back (PLAYBACK) and the bass (BASS) signals.
Bass Guitar
15TASCAM