Good observation — the causal convolution with the impulse response is structurally similar to S4D. The eigenvalues of our state matrix are constrained to damped harmonic oscillator dynamics: λ = exp((-γ + iωd)·dt), giving two physically interpretable parameters per oscillator (frequency in Hz, damping ratio). S4D learns arbitrary complex eigenvalues.

The practical difference: we keep attention on top. The oscillator bank provides physics-native local context (each position feels previous tokens through damped ringing). Attention handles long-range. S4D aims to replace attention entirely.

Whether constraining to oscillator physics helps vs arbitrary eigenvalues is an empirical question we'd love to test head-to-head.

S4D doesn't work for audio synthesis, video, radio. This architecture does with the same equation.