In this rig, audio-reactive visual motion is envelope-following only — beat-locking and onset-triggering are not available

The 4-bin FFT rig exposes bass/low-mid/high-mid/highs amplitude continuously via a.fft[0..3] (Hydra) or lo/mid/hi (Punctual). Driving motion with these values gives envelope-following reactivity: motion amplitude tracks the energy of a frequency band over time. What is NOT available: (1) tempo-locked changes that land on the beat or bar, (2) onset-detection that triggers a discrete event on each kick/snare hit. These require features the rig does not extract. The concept tempo-locked-change is marked not-yet-possible. This is a hard boundary on what AV integration means in this rig at L2.

Examples

Realizable: scale(()=>1+a.fft[0]*0.5) — size tracks bass amplitude. Not realizable: flash a strobe on each kick onset; change color on every bar boundary.

Assessment

A student wants to make a shape flash on every snare hit using the 4-bin rig. Explain why this is not possible, what they can do instead, and what hardware/software upgrade would make onset-triggering available.