MIDI timing clock messages are used to synchronize multiple MIDI devices to a single clock transmitter. The clock is typically provided by a DAW in computer-based setups and a sequencer or drum machine in hardware-only setups. Dedicated MIDI clock generators are available for more complicated setups that need tight synchronization, and some devices can convert between MIDI clock, DIN sync, and taps.
How MIDI clock works
MIDI clocks are sent out at regular intervals by a clock transmitter to one or more receivers. The transmitter controls playback and sets the tempo.
The transmitter never tells the receivers the actual tempo. Instead it sends 24 timing clock messages every quarter note (24 PPQ) and the receivers each calculate the tempo independently.
Start, stop, and continue messages are used to synchronize playback between devices. The transmitter continues sending timing clocks when it is stopped so that receivers can be ready when playback starts or continues. A start message will reset playback to the first beat, and a continue message will pick up where playback left off.
MIDI real time messages are high-priority messages that can interrupt other MIDI messages to ensure the best possible syncronization timing. However, the accuracy of the clock depends on the transmitter and any devices it passes through. It is common to have +/-1 milliseconds of jitter, with is irregular timing due to individual clock ticks arriving too early or too late. All equipment that receives MIDI clock needs to smooth out the timing to maintain a stable tempo. The smoothing algorithm needs to handle jitter, but also track sudden or gradual tempo changes accurately and naturally. Different manufacturers use different synchronization algorithms, which can lead to sloppy timing. This was more of a problem with older MIDI equipment that had slower processors and complex setups with long MIDI chains and routers. It can also be a useful technique, synchronizing multiple hardware sequencers to give each musical part a slightly different timing and feel.
Some devices do not transmit start, stop, and continue messages, so our pedals will begin synchronizing if it receives a MIDI timing clock message without a start or stop message first.
Comparison to tap tempo
Tap tempo is set by tapping quarter notes on a footswitch. It is simpler to set up, but is not synchronized to other equipment unless you are using a multi-pedal tap tempo controllers. Tap tempo controllers have an electronic switch on each output that simulates a footswitch press.
Neither tap tempo nor MIDI timing clock sends tempo information. The pedal calculates the tempo from the input and adjusts to tempo changes. Because MIDI timing clock sends 24 clock ticks per quarter note instead of 1 tap per quarter note, it enables tighter synchronization between equipment.
Note divisions for our pedals' parameters are configured the same way for tap tempo and MIDI clock, so you can switch between methods for recording and live use.
Configuring your pedal for MIDI clock
In the web editor's Config tab, set Receive MIDI Clock to On. You can also send MIDI continuous controller #110 to the pedal with a value of 64-127. The MIDI clock setting is remembered when power is turned off.
See your pedal's Owner's Manual for detailed information.