I made this to quickly explain to a friend what “cutoff” and “resonance” of a low-pass filter mean. The top view is a spectrogram of the sound (loud sounds are dark, high-frequency sounds appear near the top). Thought I might as well upload it here in case anyone can benefit from it.
Putting sound through a low-pass filter and modifying the filter’s cutoff and resonance has these basic effects.
The sound is a simple MIDI played on the Roland SC-88Pro synthesizer (which only has a low-pass filter, rather than high-pass, band-pass or comb).