0018. An open tempo-sync protocol of our own

• Status: accepted
• Date: 2026-10-02

Context

Shared tempo, beat and phase between devices is essential for live music and for many other music applications. The best-known solution, Ableton Link, is licensed GPL-2.0-or-later or under a proprietary licence, works on IP networks only, and does not use a PTP clock where one exists.

Decision

The framework defines its own open sync protocol and sync core (sync.md), written from public concepts and standards: masterless sessions with deterministic merge, phase alignment by quantum, NTP-style clock estimation, PTP time used directly when available (sample-aligned on wired AES67-class networks), and links over UDP multicast and unicast, Bluetooth LE, USB/serial, a WebSocket relay for browsers and the internet, and a MIDI clock bridge. Sessions can be authenticated. An optional adapter bridges to Ableton Link in builds where its licence applies.

Consequences

• Tempo sync carries the framework’s licence and works on all five platforms and in the browser.
• Wired PTP rigs get sample-accurate sync instead of millisecond sync.
• The protocol is published as an open specification for other software and hardware.