At its most basic level, a clock or timecode is used to transmit information about the tempo or position of your track. From an audio perspective, we're mainly interested in synchronizing pieces of audio equipment for timing purposes, so we're going to be taking a look at all the most important standards and ways in which timecode can make your life easier. In the '80s and '90s, timecode could be a bit of a minefield.

Thankfully it's not as complex as it used to be, but it still finds a huge variety of uses in studio gear and it's now a fundamental part of a lot of DJ equipment.

To understand the roots of timecode, we need to look to the world of motion pictures and go back all the way to the pre-video era. Although we're going to try and avoid looking at the audio-visual industry too much in this article, timecode is inextricably linked to the AV world thanks to the fact that so many of the standards we've used over the years have been developed alongside video synchronization standards.

Before video, film time stamps were relatively simple visual indicators of the position on a film, similar to those used along the edge of a photographic film to indicate frame positions. The arrival of video recording in the 1950s eventually led to the invention of automated editing systems, which required a reference point so they could analyze the position of the tape.

The need for a more advanced timecode system led to a number of methods being tried before the video industry settled on the SMPTE system, introduced in the late 1960s and standardized in 1972. The SMPTE (Society of Motion Picture and Television Engineers, usually pronounced 'simply') standard assigns a unique reference number to each frame of video, creating a standard reference for the position of the tape. Given the frame rate, equipment can easily calculate the tape's position relative to a pre-defined zero point.

There are more standards and confusing acronyms for audio-visual timecode than you'd ever care to remember (LTC, VITC, BITC, CTL, RCTC ... ), but thankfully they're largely irrelevant to musicians unless we happen to find ourselves editing a video.

Nevertheless, we should be grateful to the AV industry for the invention of one of the most important synchronization protocols, as it soon crossed over to the audio recording industry.

SMPTE very quickly caught on as a synchronization method for multi-track tape machines in recording studios. The last track on the tape was typically recorded ('striped') with timecode as a matter of course, and the SMPTE timecode not only provided a reference of the position of the tape, but could also be used to synchronize the speeds and positions of multiple pieces of equipment.

The 1980s revolution in digital music was accompanied by an increasing reliance on the synchronization of multiple pieces of equipment, from drum machines to sequencers, computers and tape machines to synths. A number of basic synchronization formats, such as Roland's DIN sync system, allowed equipment to be locked into sync, but the arrival of MIDI finally allowed equipment to be controlled remotely using standardized signals, making things a little easier (if not necessarily simple).

The MIDI protocol allows for the use of a number of different signals to control and synchronize equipment. The most common is probably MIDI clock (also known as MIDI beat clock), a very basic signal which includes tempo information and start/stop/continue messages. Although it's not particularly sophisticated, MIDI clock is more than suitable for achieving a basic level of synchronization between pieces of equipment and unlike the more advanced MIDI timecode it has the advantage of allowing variations in tempo. The one major weakness is that MIDI clock contains no location data (an indicator of position based on minutes and seconds or bars and beats) so the equipment you're synchronizing has no idea where you are in your song. To include this information, song position pointer (SPP) may be transmitted along with the MIDI clock signal.

The more advanced MIDI timecode signal, essentially a SMPTE signal converted to MIDI format, was typically used for synchronizing MIDI equipment with tape machines. In the days of multi-track tape recording, this was particularly useful because it allowed tracks to be kept clear until the final mixdown. Rather than recording each MIDI part to tape and using up valuable space, all MIDI instruments could be synchronized to the SMPTE signal and played back live along with the other tracks on the tape. Typically, MIDI equipment is synced to the tape machine rather than the other way round (which would be 

possible m theory but much less reliable).

SMPTE and the various MIDI formats reigned supreme until the mid-1990s but there hasn't really been on the agenda for the majority of musicians and producers since the arrival of more advanced computer-based setups. In large part, this is due to the fact that most of us aren't using the same kind of equipment any more - DAWs have replaced tape machines, software has replaced hardware sequencers, improved MIDI functionality has made triggering remote hardware easier, and many pieces of equipment have been replaced With effects plug-ins and soft synths.

Other forms of timecode still exist, most notably in digital signals which may contain embedded timecode information to provide a reference for equipment, while you could argue that a digital word clock is a form of timecode sync signal.

One of the most common (and probably most interesting) contemporary uses of timecode signals exists in computer-based DJing setups. The OJ world has been revolutionized over the last ten years by the emergence of vinyl emu I at ion software such as Serato Scratch, Native Instruments Traktor Scratch and Atomix VirtuaiDJ. These programs allow virtual DJing environment to be created in software, with audio files manipulated, pitch shifted and controlled via a vinyl record encoded with a timecode signal. The timecode from the control vinyl is sent (as an audio signal) to a soundcard connected to the computer. The software decodes the signal in order to analyze exactly what you're doing to the control vinyl, and then uses this information to synchronize the audio Signal playback with the vinyl. Slowing down the turntable Will slow down the track, pulling back the record will reverse the playback, and so on.

Tracks can be chosen from your library of audio files and played back as if they were on the turntable.

The latest software is so accurate and responsive that complex scratches can be carried out in addition to more basic mixing and beat-matching. There are a huge number of advantages to this approach, from the simple fact that you no longer need to carry as many records, to the ability to mix and scratch with tracks that aren't available on vinyl. The fact that the control vinyl can be played on any regular turntable not only means that the setup feels comfortable and familiar for DJs weaned on vinyl, but also that the setup is relatively portable and flexible. Hook your laptop up to any club's equipment. slap the control vinyl on the turntables and you've instantly got all your digital music collection at your disposal.

On a slightly different level work on a similar principle, except that rather than using an audio signal sent between devices to control the playback of a track, all control signals are contained within the one box. Things are slightly more complicated due to the fact that the music is being played back from a regular PCM stream on an audio CD, but the overall operating principle is similar. In comparison to using turntables and vinyl records, vinyl emulation software and CDJs might be a little more complex but they offer a great deal more flexibility and advanced sound manipulation options such as looping, pre-defined cue points and time stretching. Reliability, sound quality and accuracy are now at such a high standard that you'd be foolish not to consider adding one of these options to your DJing setup.

In a word, no, timecode is no longer something most of us should need to worry about. The majority of timecode information is handled behind the scenes in a modern DAW-based setup. The majority of us probably don't even come close to using MIDI to its full potential for synchronization, which is a testament to the simplicity and convenience of more modern approaches.

I would hazard a guess that fewer than one in a thousand of us even considers SMPTE as part of a home project studio setup. Nevertheless, the various timecode systems remain perfectly usable in a modern studio environment and you'll be grateful for them m the event that you need to sync an older piece of gear or a tape machine with your modern equipment.