I have used PSR2000 with TRITON.

To play AA parts from PSR or QY on an external source, you need to do lot of housekeeping and organisation.

There are several ways you can do this.
1. Edit the style on PSR and QY and delete XG program change messages from the header. And then insert program change messages for your module. MSB and LSB numbers.. Controller settings etc.

2. This is easier to manage. You do not need to change the style. But you create a performance setup on the external module for each style you will use.
Edit each channel sound the way you want. Then filter out MIDI program change messages on the external module. So even if you PSR or QY is sending out program changes... your module will ignore it.

I used the second method on TRITON. You can have 200 song setups in a SNG file. So I could have setup for upto 200 styles.

Hope this helps.