The main features of the omnichord are the organ like chord instrument together with the unique sonic strings, which are triggered using one of the 36 soft buttons (denoting each of the major, minor and 7th chords) and the strumplate.
I sold my Omnichord OM84 for a frankly crazy amount of money on eBay last year but not before recording some samples. Here is the first of my resultant PCMSynth presets, the simple lead sound. Don't worry, it gets better!
If you don't know what an Omnichord sounds like then check out YouTube!