Proof of concept — Max MSP → Web Audio · 3D
Same patch as Fig 3.44 — two oscillators, resonant lowpass, twin ADSRs. The flat spectrum from before, now with a time axis. Each note's harmonic stack rings out into depth as it decays.
The flat spectrum is one slice of time — just now. The waterfall shows that slice and the previous ~1.3 seconds receding into depth. You can see the shape of an ADSR envelope drawn into the surface.
Hold a note. Watch the front edge bloom on the attack, settle into a sustained ridge while you hold, then fall away into a long release tail that recedes into depth. Let go: the colour-ridge keeps glowing for almost two seconds as the release rolls back through time.
Drag vertically while you hold — that morphs the timbre between Osc 1 (the slide-down target, sine by default) and Osc 2 (slide-up target, sawtooth by default). With the default pair, pulling down on a key collapses the stack to just the plum fundamental; pulling up grows the full saw harmonic ladder up into the orange/gold.
The surface is a 128 × 80 vertex grid. Height is FFT magnitude. Depth is time. And colour is frequency, on the thermal palette real audio software uses — deep indigo at the sub-bass end, plum and crimson through the bass, vermillion and burnt orange through the mids, gold at the top.
So bass energy reads as a heavy purple-red ridge on the left. The fundamental of a C3 note (130 Hz) sits in plum. The 2–4 kHz presence band glows orange. Brilliance above 8 kHz sparkles gold.
Magnitude also fades the saturation, so silent regions melt into the paper rather than colouring it — only where there's energy does the colour come up.