Back to my Original Post,
Firstly I think it depends on the Actual Accordion sound begin used, it is being played as a solo instrument or an ensemble. But as a Solo Instrument the Accordion seems to work well with strings such as Violin, Pad Sounds, and Vocal Sounds such as choirs, another sound that works well is a piano sound.
These are my findings so far.
_________________________
Gem Wk4, Solton Ms60, Technics Kn5000, Korg Pa50sd, Yamaha Psr k1, Tyros 4, Korg Pa700