MIDI Clock Output
MIDI Clock is a 24 PPQ (pulses per quarter note) tempo signal carried over MIDI. Unlike MTC, it carries no timecode position — only a beat rate taken from the BPM. It is the standard way to sync tempo-based gear: synthesizers, drum machines, delay effects, loopers, and lighting systems that follow a musical beat.
Enabling MIDI Clock
Open Settings → Outputs and tick MIDI Clock Output. The checkbox is disabled until an MTC port is selected, and the row shows "Select MTC port to enable clock". MIDI Clock uses the same port as MTC — choose it in Settings → Devices → MTC Output (MIDI).
BPM source
Once the clock is on, the BPM Source menu offers three ways to set the tempo:
- Auto Detect — LTCast keeps estimating the tempo while the song plays. Every 3 seconds it analyses about 10 seconds of audio around the playhead (onset detection plus autocorrelation, in the range 60–200 BPM) and the detected value appears in the menu and beside the TAP button. With this source the running clock follows the estimate, so the tempo can change during a song. It works well for music with a steady beat and can be unreliable for ambient, live or rubato recordings — check it against the track before you rely on it in a show. If no tempo can be detected there is no clock.
- Tap Tempo — tap the TAP button in the bar above the timecode display in time with the music. LTCast averages the last twelve taps (the history resets after 2.5 seconds without a tap) and the result appears beside TAP. Reset clears it. The tapped value stays constant until you tap again.
- Manual — type a fixed BPM from 20 to 300 into the field that appears. Use this when you know the exact tempo from the production notes. It is the most predictable option for tempo-locked productions.
MIDI Clock BPM and LTC timecode are independent systems. LTC is frame-accurate SMPTE timecode; MIDI Clock is a musical tempo grid. A song's tempo map (changing BPM sections) cannot be represented — Tap and Manual send one constant BPM, and Auto Detect only follows the tempo LTCast estimates as it goes.
Start and Stop
The clock runs only while a song is playing:
- LTCast sends Start (0xFA), then the clock pulses, when playback starts or resumes after a pause.
- LTCast sends Stop (0xFC) when you pause, stop, press Panic, or when the MIDI port disappears.
- LTCast never sends Continue (0xFB). Resuming after a pause sends Start again, so a drum machine or sequencer restarts from the top of its pattern. Seeking while the song plays does not send a new Start.
Most hardware synthesizers and drum machines follow Start/Stop automatically; check your device's manual to confirm it responds to external MIDI Clock.
If a delay or reverb effect is drifting from the beat, verify that the effect is set to receive external MIDI Clock (not its internal clock) and that the MIDI cable or virtual port is connected before starting playback. Devices that receive Clock while already running will gradually drift back into sync; for clean sync, stop and restart the device while LTCast is already sending Clock.