You asked "Not sure I understand why you say " ...you have to know the arrangement very well, since the backing is rigid." How so?
It's because the arrangement is fixed within the Sequencer - ie the number of times the individual phrases were played (Verses & Choruses), when key changes are made, when tempo changes are made, when the Ending kicks in etc. All these things have to be remembered when you are playing along with a previously recorded song in the Sequencer, otherwise you may end up playing the wrong melody part with the sequencer accompaniment
If a sequnce is recorded by following the written 'dots' and then you use the same 'dots' when playing back, then the problem probably wouldn't exist. However, since I don't use 'dots', I have to remember the actual arrangement I used, when I recorded the Sequence.......
Other advantages of using the Sequencer on some songs, during a live performance are :
1. You already know that the chord progression for the entire song is correct, since you will have presumably carried out any necessary editing, to ensure that it is correct.
2. All the Control changes are taken care of within the sequencer - ie sounds, Technichord, Panel Memory, Performance Pads etc., which leaves you free to concentrate on the melody parts - particularly if you are like me and don't read..........
I only use this method for some of the songs I play, which for reasons of authenticity, require a 'backing' which cannot be reasonably achieved in the Composer. The greatest majority of songs which I play during a live performance, use the more conventional method of 'backing' provided by either Built-In styles or my own Composer styles.
[This message has been edited by Bill Norrie (edited 06-21-2009).]