I just recently started working with my ES 8 recording song tracks.  My goal is to play songs at live gigs with myself and a guitar player playing along with the songs.  I have been reading through the forum Q&As;. So far it sounds like utilizing master mode is something I should learn how to do.  I love the capability to assign tracks to seperate channels so I can run the bass track to a bass amp and other tracks to other seperate speakers.  But I am very new to this.  I would welcome any suggestions on the best way to utilize the ES 8 to accomplish my live performance goal.  Thank you in advance.

The assignment of a PART, like the bass, to an assignable output would take place while editing the SONG MIXING program (it is not a function of the MASTER mode). This is just FYI: there are a lot of good reasons to learn about MASTER mode, but you do not need it in order to assign your Bass PART to its own output.
It takes place in the SONG MIXING program.

From [MIXING]
Press [EDIT]
Press the number of the PART you want to route to an output
Press [F2] OUTPUT
Press [SF3] SELECT
the normal setting is L&R;- which routes the PART to the main left and right output. Here you can select the Assignable L ("asL"), Assignable R ("asR"), or the Assignable Left/Right ("asLR")

When you route a PART to an assignable output it is removed from the main SYSTEM, but it can maintain its INSERTION EFFECTS if any are applied to the PART.