5 neons in a ring counter type set up with a pot and cap value change for each stage,
a multivibrator modulator w/ 2 neons – rate pot, shape pot – range switch, switch o/off to ring counter.
different one w/out shape pot or range switch – depth pot – switch to power it from b+ or the previous multivibrator and switch on/off to the ring counter.
a third single neon osc as modulator w/ just rate pot, switch from b+ or previous modulator, on/off to ring counter
subosc divider, i grabbed from your vco circuit i believe, w/ a range switch,
and a 12 stage passive low pass filter (the magic part)