Pressure-sensitive ribbon-controller subharmonic oscillator vacuum tube synthesizer dating back to 1929. “Tongues” can be used for fixed pitches.
I’ve read a lot about early electronic instruments but I think this was new to me. Heard about it from a link someone posted in a Facebook discussion about Hindemith:
Custom-built Trautoniums, including a CV/gate model for use with modular synths:
LudoWic explains how to use the metal tabs, though he himself uses only the wires. Also seems clear from his comments that the “subharmonics” are really used as chords.
Watching a few videos I was interested to see that Oskar Sala kept upgrading to more modern versions of the instrument.
I saw a trautonium concert last year in Munich! The videos above are private unfortunately.Edit: Not private, you just have to switch to Youtube. Neat!