A preamp is definitely needed. I assume your modules are multi timbral. If they are it's easy. You basically only set the channels you need to recieve. You would hook both modules up to your sequencer in a daisy chain. For example, since you would set the drums on one module to recieve on channel 10. Then you would turn off all of the channels that you are not using. Then you would set all the other channels on your other module to recieve as needed. You could put your bass one channel one, strings on channel two, etc etc. you could also layer your sounds in this wasy. For example, have a piano on one of the 16 tracks and have a string on another track, but set both of thier recieve channels to 1. Then, you would hear both sounds playing whatever sequence you have on channel one. You can also layer sounds from the different modules in this manner. Have the bass on one module set to recieve on channel 2, and have the strings on the other module also recieving on channel 2. I hope this was clear enough for you. Good luck.