The Hydra rig shim exposes only 4 FFT bins — onset, tempo, RMS and spectral centroid do not exist

The rig’s Hydra audio shim provides only the four raw FFT bins. Higher-level audio features that native Hydra or richer bridges expose — onset detection, tempo/beat-phase, RMS/loudness, spectral centroid, and per-instrument sidechain — are absent here. You cannot author reactivity that depends on them; a mapping must be built from the four bins alone (e.g. thresholding a bin as a pseudo-onset). This boundary is what the AV-bridge doc means by the 4-bin contract.

Examples

// Not available: onset, tempo/beat-phase, RMS, spectral centroid, per-instrument sidechain // Pseudo-onset from a bin threshold: () => (a.fft[0] > 0.6 ? 1 : 0)

Assessment

A performer wants visuals to flash on each kick using an onset feature. Explain why the rig shim can’t provide onset directly and sketch a 4-bin workaround.