Here's a bit of organ history from about 1985. The Genius series of Lowrey organs had a cartridge slot to expand the rhythms and styles available. At one point they released a Christmas Song cartridge.
This is my Lowrey GX-225 playing the music, not me. All voices in these organs were digitally controlled analog.
This is almost 18 minutes of music.
https://app.box.com/s/r5rbrh7hrydd64wgq6w7ohgyios0p1x4