Common Time
A protocol for making independent clients agree on musical time¶
Common Time is a network protocol that synchronises the playback of pre-loaded audio across independent devices. No audio and no note data cross the wire — only an immutable anchor instant, integer ticks and transport commands. The system guarantees exact synchronisation, with no rounding error.
This page derives its own tick from a fixed anchor — 13 September 2026, 00:00 UTC — using integer arithmetic and floored division, exactly as a client must (N14). A client does the same in the background, entirely without audio.
The ceiling on timekeeping is 9 007 199 254 740 991: a tick has to fit in 53 bits, because numbers in JSON are handled as floating point (N12). At the present tempo of 118 BPM that limit holds unbroken for roughly 151 000 years.
Where to start¶
| §1 · What crosses the wire | What the protocol carries, and what it never does |
| §2 · Anchor and ticks | One anchor, immutable tempo, integer time |
| §4 · Messages | Ten messages, five operations |
| §6 · Obligations | What an implementation must achieve |
| Status | What is measured and what is not |
| The ask | Why a third implementation is worth the most |
| Documents | The specification and everything around it |