Assignment 8 is to imitate the sound of a classical modular analog synthesizer doing what it does best: subtractive synthesis. This is just a term for putting a sound (usually stable, either periodic or noisy) through one or more filters to "filter out" or "subtract" certain ranges of frequencies in favor of others. In practice the filters used were often "resonant" meaning that there was a peak in the frequency response that could be described in terms of center frequency and "Q".

Specifically, the assignment is to make a sequence of pitches, either random or in a repeating figure, and play "notes" at those frequencies by shaping them with the "vcf" filter in Pd. This filter has two outputs, roughly corresponding to the resonant low-pass and band-pass filters from the days of analog subtractive synthesis.

To generate the pitches you could use FM or waveshaping or (as I did), confect a triangle wave which you could simply draw into a wavetable or make using arithmetic operations on a sawtooth wave (that would be harder but more exactly controllable).

Every time the pitch of the oscillator is changed, you also want to generate an "envelope" (such as you needed to shape the amplitudes of the sinusoids in assignment 5). But unlike assignment 5 you need not make this patch polyphonic; classical analog synthesizers weren't.

In (my example the center frequiency ranged from MIDI 80 down to MIDI 40 over the length of each note. I didn't apply any enveloping to the amplitude, but just let the filter do all the work.

For extra credit, try to imitate the hook for Devo's rendition of the song "Coal Mine" (video available on Youtube if you want to see the original). The two most salient things happening are a sequenced subtractive pitched sequence (as described above) and a second "voice" that's filtered white noise, simply repeating the same thing every step. Here's my attempt.