1981 Suzuki Omnichord OM-27 Mk 1

This is the rarer, simpler, more limited, original, Mk 1 version with brown plastic, rough strumplate and bump next to strumplate. You can combine rhythms by pressing multiple buttons at the same time (you can't do this on subsequent models). The output jack is mono. If you insert an instrument cable in the output jack, it does not defeat the internal speakers (like on the OM-27 Mk 2 and other Omnichords). There is no mechanism in the original OM-27 output jack to disconnect the speaker. Also, the strumplate on the Mk 1 is monophonic. If you touch two sections of the strumplate at once, no sound.
The OM-27 was the first Omnichord model (from 1981) and is the simplest. It features 27 chords (9 keys x 3 variations (major, minor, minor 7th (eg. C7)). Unlike subsequent models, if you press more than one button button in a key, you don't get other chord variations. The G major button has priority over all others.
Daniel Lanois used an OM-27 on many productions including U2's The Joshua Tree (1987) album. "Love Is a Stranger" (1983) by Eurythmics features chords and Sonic Strings from the OM-27.