Dan,
i think you need and you most read Roland MIDI Implementation,
here you can download:
Roland VA-76 (Roland VA-5, VA-7 ,and VA-76 has the same arranger eingine)
VA-76 MIDI Implementation (VA-76_MI.pdf)
VA-76 Owners Manual (VA-76_OM.pdf)
http://www.rolandus.com/products/productdetails.php?ProductId=284and here:
G-70 Version 2 Manual (PDF)
http://www.rolandus.com/products/productdetails.php?ProductId=656and E80:
E-80 MIDI Implementation (E-80_MI.pdf)
E-80 Owners Manual (E-80_OM.pdf)
http://www.rolandus.com/products/productdetails.php?ProductId=825and Dan your software need a style Sequencer with its own format too (maybe MIDI format with Markers recognition for intro-fills-variation-ends):
8-intro
8-variations
8-fills
8-Ends
-and one special guitar track (when you change chords the guitar track, change the chord like a real Guitar Chord Scale)
-and also:
1 track for loops slices (played through a midi midi sequence):
8-intro sliced loops (8 midi sequences)
8-variations sliced loops (8 midi sequences)
8-fills (8 midi sequences)
8-Ends (8 midi sequences)
and if you can not make a style Sequencer, then support for
MIDI style with markers and one track for special Guitar track and one for midi sequences for sliced loops will also be good.
then style creators can use third party Sequencer for styles,
and for slices ReCycle:
http://www.propellerheads.se/products/recycle/