Tempo sync
Lock the musical clock to an external tempo: Ableton Link, a tapped tempo, or a host that provides one.
A musical clock counts beats, bars and tempo in BPM. Everything tempo-aware reads from it: sequencers, beat-synced LFOs, anything keyed in musical time. Tempo sync is the choice of where that clock gets its beat.
How beats relate to frames and audio time is covered in Clocks & tempo.
Setting the tempo
Add a Score node. It is found by walking the graph rather than by wiring, the same way Canvas and Render Settings are, so dropping one anywhere sets the tempo for the project. With no Score node the clock runs at 120 BPM in 4/4, the timeline's BPM and time-signature fields refuse edits, and there is nowhere to choose a source.
Score carries bpm, the time signature, swing, and the musical key and scale. It also carries tempo_source, which is the choice this page is about. Its beat, bar and beat_phase outputs can be wired like any other value.
Tempo sources
One source is active at a time. Pick it on the Score node's tempo_source dropdown, or cycle it with Cmd+Shift+T.
Manual: the built-in tempo. Set a BPM and it holds. This is the default.
Tap Tempo: press
Cmd+Tin time. Two taps give a reading; it takes the median of the last seven intervals, clamps the result to 20 to 400 BPM, and starts a fresh set of taps after a four-second gap.Ableton Link: the local network's shared tempo. Any Link-enabled app or device on the same network shares one tempo and phase, so playback starts already in step with the room.
MIDI Clock: the 24-pulses-per-beat clock from external hardware or a DAW.
MTC (MIDI Time Code): SMPTE timecode delivered over MIDI.
CLAP Host: the transport of the host application, when DNA is running as an audio plugin.
Both decoders are written and neither is fed. The MIDI input parser discards system real-time bytes, including the 0xF8 clock tick, before anything can count them, and the MTC driver returns nothing to the tempo bus by design because timecode carries position rather than tempo. Selecting either source leaves the clock holding its last known tempo. Use Ableton Link or a tapped tempo.
How it reaches the graph
Whichever source is picked, the whole graph reads one tempo. The musical clock is ambient, so a tempo-aware node works as soon as a source is locked.
Beat globals are not ambient everywhere. $BPM, $BEAT, $BAR and $BEAT_PHASE resolve inside an Expression, which runs per element on the GPU. A parameter formula is evaluated on the CPU and reads all four as 0. To drive a parameter from the beat, wire it from a node that reads the clock rather than typing a formula. See Parameter expressions.
Ableton Link also reaches the graph as a node. Ableton Link outputs bpm, beat, phase, peers and is_playing as ordinary values you can wire anywhere, independently of what the tempo source is set to.
Stable sync
Keep Link machines on the same local network. Link negotiates over the network rather than over a cable, so a busy or segmented venue network is the thing most likely to break it.
Tap tempo reads the middle interval rather than an average, so one stray tap is discarded rather than dragging the reading. Give it four or five steady hits.