I need help on hooking a midi accordion up to the sd1.

Here is what I want to do... On the right hand of the accordion I want to permantly have a mussette sound and the chords of the left hand of the accordion I want to control the arranger. What is happening when in accordion mode, If I change the sound on the keyboard it mirrors it on the accordion which is no good. On the other hand, If I use the GM midi I get the permanant mussette sound on the accordion but my chords will not control the arranger. It seems that I can have one or the other, but not both.

This application seems too basic. What am I not doing?
Please advise,
Herb