I looked closely and realised they're using the Formant analogue synth, from Elektor magazine! I wanted to build this when I was in my early teens! I still have (some of) the original Elektor magazines.
Wow! Just WOW!
I love you too! You're my man. #nohomo
this Elektor Formant Synth is a beast! had plans too to DIY but the Formant Pro from Hans-Joachim Helmstedt.