MIDI beat clock (also known as MIDI timing clock or simply MIDI clock) is a clock signal that is broadcast via MIDI to ensure that several MIDI-enabled devices such as a synthesizer or music sequencer stay in synchronization. It is not MIDI timecode.
Unlike MIDI timecode, the MIDI beat clock is tempo-dependent. Clock events are sent at a rate of 24 ppqn (pulses per quarter note). Those pulses are used to maintain a synchronized tempo for synthesizers that have BPM-dependent voices and also for arpeggiator synchronization. It does not transmit any location information (bar number or time code) and so must be used in conjunction with a positional reference (such as timecode) for complete sync.
Because of limitations in MIDI and synthesizers, devices driven by MIDI beatclock are often subject to clock drift. For this reason, it is a common practice on equipment that supports another clock source such as ADAT or wordclock to use both that source and MIDI beatclock.
MIDI beat clock defines the following real time messages:
- clock (decimal 248, hex 0xF8)
- start (decimal 250, hex 0xFA)
- continue (decimal 251, hex 0xFB)
- stop (decimal 252, hex 0xFC)
See also [link]
External links [link]
https://wn.com/MIDI_beat_clock
MIDI timecode
MIDI time code (MTC), or MIDI time division, embeds the same timing information as standard SMPTE timecode as a series of small 'quarter-frame' MIDI messages. There is no provision for the user bits in the standard MIDI time code messages, and SysEx messages are used to carry this information instead. The quarter-frame messages are transmitted in a sequence of eight messages, thus a complete timecode value is specified every two frames. If the MIDI data stream is running close to capacity, the MTC data may arrive a little behind schedule which has the effect of introducing a small amount of jitter. In order to avoid this it is ideal to use a completely separate MIDI port for MTC data. Larger full-frame messages, which encapsulate a frame worth of timecode in a single message, are used to locate to a time while timecode is not running.
Unlike standard SMPTE timecode, MIDI timecode's quarter-frame and full-frame messages carry a two-bit flag value that identifies the rate of the timecode, specifying it as either:
