MIDI 101
Today we take communication between electronic instruments for granted. Before MIDI (or Musical Instrument Digital Interface, if you didn’t know), getting bits of hardware to talk to each other was tricky at best, and quite often simply impossible. Electronic instrument manufacturers sometimes provided ways to make their own devices talk to each other – for example, some Roland sequencers could be synchronised to some Roland drum machines – but if you wanted to sync that same sequencer up to a Korg beatbox? Forget it. Even triggering one synth from another made by a different company was nigh-on impossible.
As synthesisers and sequencers came under digital control, the situation became untenable. A few companies devised their own protocols for interconnecting these complex instruments – for example, Oberheim’s OB-X and OB-Xa synthesisers could be connected to the company’s own DSX sequencer using the ‘Oberheim Parallel Buss’; and PPG’s synths could be connected to their own Waveterm computer using the ‘PPG Communication Bus’. However, a PPG synth could not be connected to one of Oberheim’s instruments.
Into this quagmire stepped Sequential Circuits’ Dave Smith who, along with engineer Chet Wood, concocted a universal interface for synthesisers. The idea harkened back to June of 1981, when it was first proposed to Tom Oberheim by Roland founder Ikutaro Kakehashi.
By the Winter NAMM of 1983, all the major manufacturers of electronic musical instruments had signed onto the idea, and it was at this convention that Smith unveiled Sequential’s new Prophet-600 synth, complete with newfangled MIDI connectors around the back – the potential of which was demonstrated by plugging it into a MIDI-equipped Roland Jupiter-6.
Getting the max from MIDI
Musicians of the time were thrilled with the idea of playing two disparate synthesisers from a single keyboard. Yet, to their credit, the clever bods who made up the MIDI Manufacturers’ Association were wildly forward-thinking, and included support for things like note-off, velocity, aftertouch, program change and much more. MIDI messages can be sent on any of up to sixteen channels allowing for control over multiple instruments at once, or multitimbral instruments.
MIDI is connected via three jacks – MIDI In, MIDI Out and MIDI Thru, the latter of which simply passes the input to any other device plugged into this jack, as a means of daisy-chaining multiple devices.
Two of the most important types of MIDI information are MIDI Continuous Controller (or MIDI CC) messages and SysEx data.
Up to 128 (numbered 0-127) MIDI Continuous Controller messages can be used to control individual parameters that change smoothly and gradually over time – a filter’s cutoff frequency, for example. This allows the hardware knobs, wheels, and pedals of one device to control the parameters of another. It also allows us to automate such control – something we take for granted today. Some MIDI CCs are defined in the MIDI standard – Pan is 10, for example, while Monophonic Mode is activated with CC 126. Others are unassigned.
SysEx, meanwhile, is short for ‘Systems Exclusive’, a MIDI message format that allows manufacturers to implement proprietary MIDI messages exclusive to their own devices, each of which is given a unique SysEx ID. Using SysEx messages, the entire state of a device may be transferred to another device of the same model, allowing users to save, store and swap patch data between two units, much as a VST instrument’s patches may be stored and recalled as FXP files. SysEx also facilitates using software to edit the patches of a given instrument, and over the years there have been a number of patch editors and librarians released for MIDI-compatible devices.
MIDI’s longevity is a testament to the foresight of its developers. Even in today’s virtual studio, MIDI is still used to control synths and effects. Now we have cool modern functions such as ‘MIDI Learn’ that MIDI’s original designers probably never dreamed of – even if the once-ubiquitous MIDI cable itself has given way to USB, LAN and Wi-Fi transfer.
“Even in today’s virtual studio, MIDI is still used to control synths and effects”