Source "MIDI clock tempo"
This source reacts to incoming MIDI clock (MTC) tempo messages. These are metronome-beat-like messages which can be regularly transmitted by some DAWs and MIDI devices. The frequency with which this message is sent dictates the tempo.
The higher the calculated tempo, the higher the absolute control value. A tempo of 1 bpm will be translated to a control value of 0%, a tempo of 960 bpm to 100% (this corresponds to REAPER’s supported tempo range).
This source can be used in combination with the Target "Project: Set tempo" to obtain a "poor man’s" tempo synchronization.
Be aware: MIDI clock naturally suffers from certain inaccuracies and latencies - that’s an issue inherent to the nature of the MIDI clock protocol itself. E.g. it’s not really suitable if you need super accurate and instant tempo synchronization. Additionally, ReaLearn’s algorithm for calculating the tempo could probably be improved (that’s why this source is marked as experimental).