Assembles the four ingredients of the tape sound from FFmpeg primitives. Magnetic saturation: the signal is pre-driven (+4/+8/+12 dB for gentle/medium/hot) into an oversampled tanh soft clipper (4× oversampling suppresses aliased harmonics), which compresses peaks and grows odd harmonics — the 3rd harmonic that gives drums crack and guitars edge — then post-gained back toward the input level. Frequency response: a broad bell at the head-bump frequency (+0–6 dB; the damped low-end hump real heads produce when the recorded wavelength approaches the pole-piece length) plus a high-shelf rolloff; both corners follow the tape speed, because on real machines the bump sits an octave higher each time the speed doubles (a 15 IPS machine bumps around 50–70 Hz, 30 IPS around 90–110 Hz, and slow speeds go darker sooner — 3.75 IPS rolls off above ~5.5 kHz). Wow & flutter: cascaded vibratos at 0.5–25 Hz with depths of 0.05–0.4%, the range where professional machines spec 0.02–0.1% WRMS and ears get sensitive. Tape hiss: deterministic seeded pink noise, level-set from a measured calibration so "subtle" sits a few dB under the speed’s nominal noise floor and "audible" a few above. Before/after, an FFT probe measures the bump-band lift relative to the overall level change, the harmonic growth in the 8.5–11.5 kHz zone, and RMS/crest factor deltas, and the report names every applied parameter.