MIDI Clock
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{{No footnotes, date=January 2020 MIDI beat clock, or simply MIDI clock, is a clock signal that is broadcast via
MIDI MIDI (; Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and ...
to ensure that several MIDI-enabled devices such as a
synthesizer A synthesizer (also spelled synthesiser) is an electronic musical instrument that generates audio signals. Synthesizers typically create sounds by generating waveforms through methods including subtractive synthesis, additive synthesis a ...
or
music sequencer A music sequencer (or audio sequencer or simply sequencer) is a device or application software that can record, edit, or play back music, by handling note and performance information in several forms, typically CV/Gate, MIDI, or Open Sound Co ...
stay in synchronization. Clock events are sent at a rate of 24 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. MIDI beat clock differs from
MIDI timecode MIDI time code (MTC) 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 t ...
in that MIDI beat clock is
tempo In musical terminology, tempo ( Italian, 'time'; plural ''tempos'', or ''tempi'' from the Italian plural) is the speed or pace of a given piece. In classical music, tempo is typically indicated with an instruction at the start of a piece (ofte ...
-dependent. Location information can be specified using MIDI Song Position Pointer (SPP, see below), although many simple MIDI devices ignore this message.


Messages

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) MIDI also specifies a System Common message called Song Position Pointer (SPP). SPP can be used in conjunction with the above realtime messages for complete sync. This message consists of 3 bytes; a status byte (decimal 242, hex 0xF2), followed by two 7-bit data bytes (least significant byte first) forming a 14-bit value which specifies the number of "MIDI beats" (1 MIDI beat = a 16th note = 6 clock pulses) since the start of the song. This message only needs to be sent once if a jump to a different position in the song is needed. Thereafter only realtime clock messages need to be sent to advance the song position one tick at a time.


See also

*
DIN sync DIN sync, also called Sync24, is a synchronization interface for electronic musical instruments. It was introduced in the early 1980s by Roland Corporation and has been superseded by MIDI. Definition and history DIN sync was introduced in t ...
* PPQN * Word clock


External links


Freeware to measure a midiclock beat signal



MIDI specification

Summary of MIDI messages

Song Position Pointer (SPP)
Encodings MIDI standards Synchronization