Peter Blasser put bounds modulation capability into many of his oscillators. But what is it? Consider an oscillator that bounces back and forth between an upper voltage and a lower voltage. Call those the bounds. Many oscillators work with fixed bound, typically -5V to +5V. But it is possible to make those bounds variable, under voltage control.

How to patch it

Only three modules are needed: a slew (of any kind, really), a comparator, and a switch. When patched as in the diagram above, the result is an oscillator that peregrinates between the upper and lower bounds. Slew rate impacts the frequency, of course, but we’re going to ignore frequency modulation and look at the impact of varying the bounds. Changing the bounds has two effects. Naturally, it changes the amplitude. But the frequency is altered at the same time, due to the fact that there is a longer or shorter distance to travel before reaching the bound.

The photo above shows a patch having three bounds modulated oscillators. I used one After Later Audio Tilt and two Joranalogue Audio Contour 1 slew generators for the slews. Comparators come from the Tromsos, and the switches from the Softwire Synthesis Octal VC switch.

The special sauce gets added by way of mixing fixed voltages with audio rate CVs obtained from Just Friends to create dynamic bounds. These are handily mixed by two Happy Nerding 3xMIA modules. In the demonstration video and audio I play around with the mixes, as well as with the frequency and shape of the Just Friends outputs. Keep in mind that no frequency modulation is applied to the slews. All FM is the result of audio rate bounds modulation.

And here is the same audio as an MP3.