I use two different methods, when playing at gigs. I go out with a guy who plays guitar and sings the 60s and 70s songs and the gigs are generally of the 'Dinner and Dance' type.
During the time the guests are eating, I generally play a selection of 'background' music - ballads, standards, evergreens etc. using either normal styles (built-in, composer or self made) and they serve the purpose well. I use the Panel memories and footswitches, more or less as described by Bob, with the set-up for each song/tune individually loaded from an SD file.

When the guests have finished eating and want to 'shake a leg', I use a different technique, when accompanying my singing guitar player. We try to get an authentic representation of each of the 60s and 70s songs, with all the 'licks' and nuances included, and this is just not possible using 'normal' 4 measure, repetative styles from any source. To this end, by listening to the original recordings, I make my own Composer style for each song, generally using 8, 12 or 16 measure Variations, with Intro, Ending and Fill-Ins if necessary. Sometimes a song 'Style' can be implemented just using the 4 Variations in Composer Bank A, but often they require additional Variations, so I use Composer B and on rare occasions - Composer C also. This entails a considerable amount of work, as you can imagine, but I enjoy the challenge and a successful outcome is very satisfying !

Having constructed all the parts of a song in the composer, I then create a Sequence, without using the Right1, Right2 and Left parts, but include the Control Track which takes care of all the Panel Memory changes, together with any Fill-In, Performance Pad, Technichord etc. triggers - no need to use footswitches or any of the Panel Controls. Since I don't use 'The Dots', this means that every performance of a song, will have an identical accompaniment - as the singer would expect - but it still leaves me free to extemporise, and add instrumental solo parts as required, using Right1, Right2 and Left voices, while the sequence is playing. So basically, I use the Sequencer and Composer, to create a complete individual 'Style' for a song. Each song set-up and sequence, is loaded from SD Card, as normal.

Most of the songs here : http://www.willumspages.co.uk/page9.html (between numbers 117 and 194, which are 60s/70s, Beatles, ABBA etc.), were created this way and are some of our songs used during gigs. They are used without the melody line, of course - since this is added as a vocal.