MIDI Beat 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, an ...
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 ...
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 Musical note, note and performance information in several forms, typically CV/Gate, MIDI, or O ...
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 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 ...
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 :en:SysEx#System Exclusive ...
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