David Brown of Lark In The Morning demonstrates the Melodihorn, a strange blown organ instrument.
Not a synth – but weird enough that it could find a place in a lot of types of music.
Blow into it and play it like a piano. Comes with both short blowpipe for hand-held playing and longer hose for tabletop play. Also has a button to the right of the keyboard which gives a vibrato effect when pushed repeatedly. Comes with a case. Sounds like an accordion.