I play the new part at 4:15
I have not really exploited this idea before - so it's about time: Changing the timbre of a square wave be letting it control another square wave by resetting its oscillator. The sound is...... well, interesting - somewhere in between a dalek and an electric guitar.
The music is again something I made back in the early 2000's and I play it on my Yamaha HE- organ, Roland SH-2000 and JX-8P synthesizers and CR-1000 drum machine.