Din Sync was developed by the Roland Corporation as a way of simplifying the synchronisation of sequencers and drum machines in the early 1980s. Prior to its introduction - the two main components for sync - start/stop and clock- were usually found as two separate sockets. Companies decided on different numbers of clock pulses that equated to a 'step' or rhythmic interval in their products - Roland 24, Linn - 48, Oberheim - 96 etc. The Din Sync concept put both the clock stream and start/stop on separate pins within a common connector and set the number of clocks per quarter note interval at 24.

Out of the ash that was Din Sync in the mid 1980s so Midi Clock was born and in 20 years not much has changed in the way electronic musicians and producers tempo-synchronise hardware and software.

Same basic principle only midi serial data replaced 5 volt pulses.

24 Pulses per quarter note. Start, Stop and Continue. 

Voltage pulses have a lot going for them. They travel at light speed and you can do cool things to them with simple hardware that has been around for a long time.

Tight tempo sync is easily achieved using voltage pulses for synchronisation. Each connected device advances one step or clock interval at the rising edge of every pulse. Think of it as well meshed sprockets in a gearbox.

Midi messages being serial data are slow in comparison and they require a lot more processing to do things to them in meaningful ways. That processing means messages have to wait their turn and if that same processing is shared across an IC that must also scan a keyboard, check for knob value changes and deal with program and control change data in real-time then it's easy to see why there are limitations.

The advantages that Midi brought with it are many and varied.

Synchronisation is not one of them.

Midi Clock pulses have no priority over any other midi message. On a single midi cable with 16 potential channels of note, velocity and duration alone it is very easy to leave no room for an uninterrupted Midi Clock stream.

Even if a Midi Clock hardware device has a dedicated IC for processing sync I/O (and this is very rare these days) most only provide a single Midi In and Out port to simultaneously synchronise and transmit/receive other performance data.

The application of Midi Clock in a modern software environment takes things into even murkier territory.

Now we find no dedicated hardware taking care of synchronisation at all. Creation and processing of Midi Clock by software that has to share resources with an OS that at any time may be busy looking after a million other tasks is never going to deliver accurate synchronisation. Early sequencing computers like the Atari with built-in midi ports and well written software running under very lean operating systems went close to rivaling good hardware sync. The current mainstream computer OS platforms are so overloaded that keeping Midi Clocks accurate is a very tall order indeed.

Midi has now morphed into USB making matters even worse.

Our simple meshed gear analogy for voltage pulse synchronisation has now become a virtual gearbox with a worn and highly unpredictable clutch.

There are some good Midi Clock devices out there and many people use older equipment and software with dedicated Midi Sync ports. Even the best of these all respond differently when synchronised. Each device or software application will start late against the master to some degree. Many devices that do manage to generate stable outgoing Midi Clock still struggle to align the outgoing clock pulses with the internal sequencer grid that should be driving it. Sometimes it is a little. More often it's a lot.

It makes composing electronic music hard work.

You lose the snap in your sequencing. 

Because the Midi Clock stream is serial data on a molded 5 pin plug we have all been stuck with this state of affairs since day one. Some software applications let you advance or retard the Midi Clock I/O but on the whole it's not a very rewarding experience. Start is generally always start and there is not much you can do about it.

Until now.

Click the Sync-Shift Mark II link above to get a closer look.