With all the posts on adding a module to keyboards recently, I came across this demo of a 1983 model from Bohm, which I thought might be fun to listen to so as to see how things have changed over the last 35 years or so. (Note: it came out the same year as Midi was introduced to the world, so it also shows how users had to play a separate module before Midi)
The unit was also available for the Bohm DS range of organs (These were totally analogue) where it was full integrated into the organ.

Enjoy

Bill