From what I see in the instructions for the Dallee sound system, you could connect that directly to the TMCC horn/bell interface board I posted about above and have TMCC controlled whistle and bell, and the motor voltage would control the prime mover sounds. It should be dirt simple to get that going.
The downside appears to be the size of these boards, they take up a lot of space! They don't give dimensions, but from this picture, I'd say each of them are at least 3" long, and with all the stuff sticking out of them, they consume a lot of space. Contrast that with the size of the ERR RailSounds commander single board that's much smaller and thinner than one of these boards, and you'll see that these are for big items!
