At its inception, the Musical Instrument Digital Interface was hailed as the saviour of the experimenting synth player, the end to all triggering and interfacing problems. However, as musician and keyboard consultant Vince S. Hill has been discovering, design inconsistencies between models have conspired to turn an elegant theory into a decidedly awkward practice.

Whether you have heard it in your local music store or read about it in reviews and adverts, you will no doubt be trying to come to terms with the latest electronic music buzzword - MIDI.

The implementation of this interface is causing a great deal of excitement in and given a welcome boost to much of the musical instrument industry, not only to musicians, but also to those designing, manufacturing, selling, and - last but not least - writing about synthesisers and their hardware and software expansions.

Broadly speaking, MIDI means communication and compatibility, or rather, should mean...

If you're thinking of changing your synthesiser or adding a new device of some sort to your electronic instrument line-up, it's more than likely that MIDI will be thrown at you as a sales feature. With a glint in his eye and a theoretical thickening of his wallet, the salesman will point to the back panel of Product X and say, 'with MIDI you can link it up to any other MIDI-equipped instrument.' He's right, of course. The five-pin DIN lead will fit any of the sockets, but what happens next?

For some musicians, having a MIDI keyboard will mean either very little or nothing at all. They're not interested in connecting more than one such instrument together, and probably haven't given the technological implications of the new system more than a passing thought. Many others, however, will doubtless be interested in taking the interface to its limits, which at this stage are a little frightening in addition to being quite exciting on paper.

MIDI is a relatively recent development and, as is so often the case with such things, its adoption has been part of a learning process on behalf of all those involved with it, not least the instruments' designers. So, given that MIDI is still very much in its infancy, I thought I'd take a look-see at some connections between different synthesisers and add-on machines to find out what can and cannot be done.

Parameter Control

The first thing to realise when looking at MIDI in relation to your own equipment (real or potential) is that it can't be used to control parameters that aren't there in the first place. MIDI can transmit and receive data relating to noteplaying, velocity and touch, but if your synth does not incorporate a velocity- or touch-sensitive keyboard it will not be capable of receiving or sending that information via MIDI.

Another simple example is that of voice numbers. If you link a six-voice polysynth to an eight-voice one, then only six voices will be received by the former and so on.

Lesson number one: although MIDI is capable of transmitting and receiving considerable quantities of data, it can't turn a low-cost synth into a fully-specified one.

Rather more disturbing than the previous - and utterly logical - limitation are the headaches many synth-players were faced with when they tried to link instruments from early MIDI batches together.

DX7-owners will probably know what I'm talking about. Most early DXs to be sold in the UK were fitted with non-standard MIDI buses. The main problem was non-acceptance of the MIDI Off command, though in addition some models could transmit keyboard information without being able to receive it, or could not understand what was being transmitted by the second instrument.

The author has tried linking a low-1 serial number DX7 with an SCI Prophet T8. Both of these synthesisers have pressure- and velocity-sensitive keyboards, but while the T8 could receive this dynamic information from the Yamaha, the Sequential flagship's attempts at transmitting the same data to the DX were met with a total lack of response. Using a later model DX7, however, communication between the two instruments was immediately successful and trouble-free.

To illustrate the problem further, connecting the early and late model DXs in turn to an SCI Drumtraks rhythm machine showed a similar discrepancy between the two generations of Yamaha instruments. Whereas the later model could play the SCI's drum sounds with full dynamics according to how hard the keyboard was struck, the earlier one could not.

Nor is this problem confined to the DX7. The cheaper Yamaha FM synth, the DX9, also suffered from the same early design inconsistency, a point that was brought home to me rather forcibly when I connected an early 9 to the first ever MIDI keyboard, the SCI Prophet 600. The Yamaha received no MIDI note-off command and each note played droned on for eternity - not a very musical effect.

If you're one of the unlucky ones who bought a non-standard MIDI DX some time last year (there's no real way of knowing which serial numbers refer to which generation of production because Yamaha's spec has gone through several changes, not all of them widely publicised), then it should be possible to get your instrument brought up-to-date by your local Yamaha stockist. If, on the other hand, you're currently thinking of buying a DX - and you've reconciled yourself to the inevitable long wait - you need have no fear because as from March of this year, all Yamaha's MIDI instruments are to the same specification as the rest of the manufacturing world's.

Thus lesson two: all MIDIs are not equal, or at least, they aren't on early Yamaha DXs.

MIDI 1, DCB 0

On a slightly different tack now, Roland's move to enable owners of instruments incorporating the earlier DCB interface to enjoy some of the benefits of MIDI by introducing their MD8 DCB-to-MIDI converter have been widely applauded elsewhere, and rightly so. However, not all in the DCB garden is rosy, as I discovered when using Roland's polyphonic DCB sequencer, the JSQ60 (reviewed elsewhere this issue). Used in conjunction with other DCB instruments such as the Juno 60 or Jupiter 8 synths, the JSQ is a well-designed and versatile digital keyboard recorder. However, used in conjunction with MIDI keyboards via the MD8 interface box, replayed sequencers were plagued by glitching, and some program patches changed their envelopes. This was true of Roland's own Jupiter 6 as well as several other models including the Korg Poly 800 and Siel Opera 6.

It would seem then that the solution for owners of DCB instruments wishing to 'go MIDI' would be to invest in the Roland MSQ700 MIDI/DCB recorder if they want to record sequences from synthesisers of both interface standards.

Even disregarding the problems of MIDI/DCB sequencing, there are signs that attempting to fuse the two standards into a cohesive, compatible network may prove rather fruitless. Simply linking a JP6 to a Juno 60 via the MD8, the Juno could not receive program changes, and could not even discern input notes when the Jupiter 6 was in Patch Preset mode.

Lesson three, then: although linking the earlier DCB standard to the MIDI one is a mildly wonderful gesture on Roland's part, technological inconsistencies will probably prevent an 'interface between interfaces' ever being more than 60% successful.

If you've read this far, you could be forgiven for thinking that MIDI is nothing other than a tale of false hopes and unfulfilled promises. In reality, though, it's because MIDI as a system can work so beautifully that so much light has been shed on its recent - and, we hope temporary - shortcomings.

Anyone who's used a touch-sensitive MIDI synth to control a compatible drum machine dynamically - as mentioned briefly above - will know how effective such a combination can sound. At present there are only two MIDI-equipped rhythm machines available (the Drumtraks and Roland's TR909) but there are plenty more in the pipeline, while MIDI keyboards with pressure and velocity sensing are now available in almost every price category. The author has found Roland's HP300 and 400 electronic pianos to give the widest dynamic range when replaying drum sounds (from both the SCI and 909) via the notes on a keyboard.

At the time of writing, it would seem that most manufacturers are in the process of bringing their MIDI specifications into line or have already done so. If you're thinking of spending a not inconsiderable sum of money on new MIDI equipment, the most obvious attitude to take remains the 'one manufacturer, one system' approach. You really can't go too far wrong if you opt for a synth/drum machine/sequencer combination in which all the components are manufactured and marketed by the same company. However, that doesn't mean to say interfacing instruments from rival makers is impossible: in many cases it is not only feasible but also very rewarding, as I discovered recently when I coaxed an SCI Six Trak into controlling a DX9, DX7, Prophet 600 and Roland JX3P.

Undoubtedly the biggest problem you'll encounter if you attempt such a link-up will be that of program selection, since not all MIDI instruments are capable of transmitting this information. However, if all you want is control of two or more MIDI instruments from one keyboard and/or synchronisation to a MIDI rhythm unit, and assuming all the instruments you're using are of recent manufacture, you should be all clear for making the most out of MIDI.

Finally, if you have a MIDI- or DCB-equipped synth that has been in your possession a while, and are now in the market for some new - fully compatible - equipment, my advice is to take your own keyboard into the shop and try it out with your potential purchase yourself just to be on the safe side. Using the shop's own example of your keyboard simply won't do, for reasons which, I hope, have become fairly clear as this article has progressed.