I came across a widget with sounds made by the same kind of old synth I have. It's a Korg Delta, which were made around 1979/80. Totally analog! It sounds really cool through my guitar FX. The sweeps in my song "Tech Support" were made using it. Widget is on the full post.
Korg Delta

Click ">" to play, the ">>" button to see the whole playlist. (not me playing any of the tracks - found the player on a site)