Rezo Haptic Metronome

Rezo started from a simple frustration: musicians with hearing loss, or anyone practicing in a noisy room, lose the click track the moment the mix gets loud. A metronome you can only hear is a metronome that fails you exactly when you need it most.

feeling the beat

Rezo is a wrist-worn haptic metronome. Instead of a click in your ear, it delivers a precise, tunable pulse against the skin — sharp enough to feel through a full band rehearsal, subtle enough to wear on stage. Tempo, subdivision, and accent pattern are all set from a companion app over Bluetooth LE.

The goal wasn't to replace the click track — it was to make it accessible to anyone, in any room, at any volume.

building the actuator

The hard part wasn't the electronics, it was the haptics. Off-the-shelf ERM motors were too mushy for anything faster than a quarter note at 160 BPM — the pulse would smear into a buzz. Switching to a linear resonant actuator, driven by a custom waveform rather than a flat DC signal, gave a crisp attack and a fast decay, so 32nd notes at tempo still read as distinct taps rather than a vibration.

An nRF52-based board handles BLE and timing, with the actuator driver isolated on its own power rail to keep radio noise out of the pulse. Battery life lands around eleven hours of continuous use, enough for a full rehearsal day.