We hope that the reasons for MIDI's existence and some of the mysteries surrounding its operation are a bit clearer after the first part of this supplement, published last month. This month we continue with a more detailed look at the more technical aspects of the system, and there's also a constructional feature by Jay Chapman that not only describes the building of a MIDI interface for the BBC Model B computer, but also explains the operation of the circuitry in such a comprehensive way that it cannot fail to be of great educational value to those interested in the workings of computer peripherals.

David Ellis takes us 'Inside MIDI' using various analogies to British Rail to explain an otherwise complicated concept in terms that most readers will be able to understand. On the other hand, it must be said that if the analogy was carried too far, some notes would not arrive at all or would turn up half a bar late!

Also by David Ellis this month is a comprehensive look at a considerable slice of the available MIDI software for popular home computers, including the Commodore 64 and the Spectrum, and this round-up should be of particular interest to anyone who is currently undecided on which computer to buy.

The BeeBMIDI interface project will be concluded over the next couple of issues, when Jay Chapman will be presenting a software package that'll enable the interface to be used as a multitrack, polyphonic sequencer with considerably greater operational capabilities than any commercially available alternative.

MIDI Confusion

When MIDI was first announced, it's probably fair to say that the lack of readily-available, updated and accurate information caused many people to expect far more of the system than was actually possible. This unfortunate state of affairs led to early disappointment when systems of interconnected MIDI products failed to behave as predicted, and this feeling of anti-climax was compounded by the sad fact that most early 'compatible' machines deviated from the agreed MIDI standard in a variety of ways.

The good news however is that as of March of this year, all MIDI machines will conform to the same specification, though that's not to say there won't still be old machines on some dealers' shelves. This is not quite so serious as it might at first appear, since most manufacturers are offering a software update service to bring older machines into line with the current MIDI specification, though this will of necessity cause some inconvenience to the unfortunate musician.

As we explained last month, you can only expect to make the fullest use of MIDI if all your machines are made by the same manufacturer, but the MIDI specification does state that a number of functions will be compatible on all MIDI keyboards, including the essential information that allows one machine to trigger the corresponding notes on another machine. In many cases, this information will be entirely adequate, though it's not inconceivable that 'specmanship' will dictate the buying habits of many users. Much the same thing has been observed in the home computer and pocket calculator markets, where the machine capable of doing complex differential equations is only ever used to add up the grocery bill.

One other slight problem that is coming to light is that designers of many MIDI-equipped instruments have forsaken conventional synchronisation facilities, meaning that many of the latest products can now be addressed only by the MIDI bus. This was true of the SCI Drumtraks, but Sequential are now providing a separate clock output in response to market demand. MIDI is undoubtedly a powerful aid to the musician and is likely to become more so in the future, but we should recognise that there is still a lot of useful non-MIDI equipment that is likely to be in circulation for some time, and my feeling is it would be wrong to cut short its life by discontinuing sync trigger facilities on new MIDI machines.