The community/tiar/osc/SelfPM object is a very low CPU bandlimited oscillator capable of generating filtered saw-ish and square-ish waveforms.
It has the classical pitch inlet and parameter.
The fbMod inlet is a positive input.
When the fbMod varies in the range [0 64], the effective fb varies in the range [fb0 fb1].
Negative fb produce squarish waveforms.
Positive fb produve sawish waveforms.
The patch tiar/synths/SelPM.axp is a simple mono synth (4% CPU) that includes an adsr amplitude envelope and an adsr fb control envelope.
Furthermore, fb0 is modulated by the aftertouch:
You can tweak the envelopes and fb0 and fb1 to get an idea of its sound range.