David Mellor revisits the instrument that started the MIDI Music hi-tech revolution. Yamaha's 16-note poly (wow!), all-digital (gasp!) DX7

The Yamaha DX7 is quite possibly the all time classic electronic keyboard instrument, the one that really set music technology in motion. Perhaps you can't remember what life was like in pre-DX7 days. Well, there was no Sound On Sound magazine for one thing — unbelievable! — and the all-mechanical Fender Rhodes piano was still considered to be a sound basis for a keyboard setup. (Widespread appreciation of the Fender Rhodes as an instrument of classic status is scheduled for some time around 1998). My own setup at the time consisted of the aforementioned Rhodes, a Casio 'organ', and an ARP Axxe monophonic analogue synthesizer. I had the Rhodes because the synths sounded totally synthetic and artificial, without any trace of human warmth. The Casio sounded terrible and offered very little tonal variation, but at least it could play eight notes at a time! The ARP Axxe, however, was a very decent single oscillator synth which I still have and occasionally use. (It's going to fetch a good price when I sell it someday because I've had it autographed by Karlheinz Stockhausen!).

When the Yamaha DX7 arrived in 1983 it turned the world of electronic keyboards upside down. It was so revolutionary that it took other manufacturers several years to catch up. The brochures were enough to make normally sensible people turn back somersaults in the streets. "16-note polyphonic", "32 memories" and lots of talk about things called "operators" and "MIDI" came right out of the blue as a total contrast to currently available synths. And for the princely sum of around £1,300 you could have one — it seemed quite a bargain even in 1983 money.

Yamaha's big breakthrough was that they had succeeded in harnessing digital technology. Whereas manufacturers of analogue synths were struggling to improve a technology which was already highly stressed, Yamaha were taking a first bold step into the technology of the future. As it happens, now that we have much more sophisticated digital synthesizers we still use the basic concepts of analogue synthesis as proposed by Robert Moog in the late 1960s. Rather than call it 'analogue synthesis', we should actually refer to 'subtractive synthesis', since the technique can be performed by analogue and digital electronics alike.

The idea is to start with a waveform which is rich in harmonics — in the old days this would be a square wave or a sawtooth — and the filter out as much of the harmonic structure of the wave as necessary. Make this filtering process dynamic, so that the timbre can vary over the duration of the note, and add variable attack, decay, sustain and release and you have what most of us would recognise as a synth. Yamaha didn't take this route with the DX7. Unfortunately, or perhaps fortunately, it wasn't practical at the time because the processing power just wasn't available to perform the complex task of subtractive synthesis. Instead they used a form of additive synthesis, licensed from its American developers, known as Frequency Modulation synthesis, or FM for short. This didn't require as much processing power as subtractive synthesis, and also offered the advantage of a whole range of completely new sonic possibilities.

When in 1983 people first heard the DX7, the general body of opinion was that its sound was very naturalistic, and while not necessarily imitating real acoustic instruments it could sound like new, non-existent, types of acoustic instrument. Of course, we now have samplers and the DX7 definitely sounds like a synthesizer to our 1990s ears. From 1983 to around 1986, virtually every record made incorporated sounds courtesy of the DX7, and naturally enough our ears eventually tired of the DX timbres, especially as we started to recognise the similarities between one DX sound and another. Roland effectively killed off the DX7's career with the introduction of the D50 — a classic instrument in its own right — which combined sampled sounds with good old subtractive synthesis, and samplers such as the Akai S900 were also getting a firm foothold in the studio.

But after a period in the doldrums, it could now be a good time for a DX renaissance, to give those once overused but recently forgotten FM sounds their proper place in our sound libraries. Let me assure you of one thing — there is a world of difference between a sample of a DX synth and the expressive qualities of a real DX synthesizer, and if you are going to use DX sounds then they had better be from the original DX7.

THE HEAVYWEIGHT

If you manage to get your hands on a real original DX7, the first thing you'll notice is now heavy it is. It's in a metal rather than a plastic case, and I'm sure there must be lead weights under the keyboard. The replacement for the DX7 — the DX7S — was much lighter but, although it corrected a number of the DX7's deficiencies and I was impressed with it at the time, the increased operational complexity didn't help it to be as usable as it might have been.

When you go searching for your classic DX7 on the secondhand market you need to be sure of two things: a) that the person who is selling it hasn't read this article and is therefore unaware of the instrument's true value; and b) that the original two ROM cartridges are present. If they are not, then the first thing you'll learn about the DX7 is that it is hard to program from scratch. You really do need to have all the original sounds available so that you can modify them to taste.

But even if the ROMs have gone missing, as they tend to with the passing of time, then all is not lost — just negotiate a lower price and check that the instrument's own program memories contain the all-important classic DX electric piano and bass sounds. These are the sounds the instrument does best — if you want synthesised strings or brass then you really should be looking elsewhere. If among the 32 presets there is at least one good electric piano and one good bass that you recognise as being at least close to the classic DX sounds then it's not difficult to modify them to get exactly the sounds you want. To program them yourself from scratch would take rather longer. The DX7 is capable of a useful range of other sounds, particularly clavichords, but I would imagine that if you have a more modern synth in your collection you will be using that where it's more appropriate.

FM THEORY

I suppose now is as good a time as any to repeat the modern legend that 95% of all DX7s returned for service still had their factory presets intact. This old story may be true (as may the one about granny on the roof rack!) but it doesn't mean that DX7s are impossible to program. It just means that when it first came out people were used to having synths festooned with knobs and buttons, and they couldn't get on with membrane switches, LCD displays and data entry sliders. Modifying an existing DX7 preset is quite straightforward if you know a little bit about what you are doing. OK, it may not be as intuitive as grabbing knobs at random and wrenching sounds into shape, but it's certainly nothing to be frightened of.

The DX7 has six oscillators, which for some reason Yamaha chose to call 'Operators' — mistake number one I reckon. Each operator produces a sine wave, which is the simplest and most basic sound possible. It is possible to use these sine waves for rudimentary additive synthesis by simply mixing all six at different levels and frequencies, but since sine waves are inherently bland and uninteresting, and you only have six to play with, this isn't likely to produce a worthwhile result. The fun really starts when you take a sine wave from one operator and modulate its frequency with a sine wave from another oscillator. This could result in a sine wave whose frequency cyclically changed up and down four or so times per second, if the frequency of the modulator is 4Hz or so, or you could set the second operator to a much higher frequency — an audible frequency in fact — which would produce a result quite unlike the original simple sine waves that they both produce. Taking this further it is possible to stack the operators so that the final output is modulated by a wave already modulated by five operators. This can create an exceedingly complex waveform. Feedback of the output of one of the operators to its input can be used to create sounds which are almost percussive in character.

The above paragraph describes the essence of FM synthesis. It's a very simple concept once you understand it and get a little practice in. Once you have the hang of controlling the frequency of one oscillator with the output of another (I'll give some hints on how to get used to this later) then you're ready to explore the different algorithms the DX7 offers. The graphics on the front panel of the DX7 show the workings of the algorithms very clearly. They also indicated that Yamaha certainly intended that the DX7 should be user-programmable, even if things didn't end up that way. The algorithm graphics show how the operators are connected. If you want an extremely complex sound then choose a tall stack of operators, one feeding into another, in which you only actually hear one or two of the operators — you hear the effect of the others through their modulating effect, but not directly. If you want a rich sound, then choose a broader arrangement where you can hear the outputs of more of the operators; you will be more limited in how you control their harmonic structure, but you can detune the audible operators ('carriers') to fatten up the sound. Perhaps the number of available algorithms (32) is off-putting to the first time user; certainly don't expect vast differences in timbres to be available from each one.

GET STUCK IN

You'll notice that the DX7 is, by modern standards, generously provided with buttons, although the data entry slider, next to the output level control, is the only 'knob'. Having a decent number of buttons means that you can go directly to the parameter you wish to edit. There's no tiresome cursor to shunt about here. First of all select the voice, from the internal memory or the cartridge, that is close to the sound you eventually want to hear. You will now have a suitable algorithm (probably) and editing will be straightforward, so press the Edit/Compare button.

A good way to start is to find out what's good and what's bad about the sound, so you know where to home in. You can do this by switching the operators on and off in turn, using the first six buttons. The display will look something like the diagram on the previous page. While you are doing this you can check with the algorithm diagram, and you'll notice that punching out an operator at the bottom of the stack takes out a whole element of the sound — or the whole sound if there is only one operator at the bottom — whereas taking out higher operators affects only the timbre.

If the voice uses feedback on one operator you'll particularly notice the effect the elimination of this operator has. From this button pushing exercise you should be able to find out which operator affects the particular quality of the sound that you would like to change.

In all probability the sound will either be too bright or not bright enough. There is no filter on the DX7, so how do we change this? You should know by now which operator is responsible for the brightness of the voice you have chosen (because the sound won't be so bright when you knock it out), so all you have to do is change the level of that operator. Increasing its level will brighten up the sound, lowering it will reduce the brightness. Press Operator Select until the one you want is indicated in the display, then press Operator Level and adjust to taste. Is this easy or is this difficult? I think most people would say it's pretty straightforward — so why does the DX7 have a reputation for being difficult? That's one of the great mysteries of music technology, but I would guess that when an instrument has a vast wealth of facilities, and the important ones are mixed up with the lesser ones, that most people just write off the whole lot as being too complicated. There's a moral in this — the easier the designers make their equipment to understand and operate, the more benefit people will get out of it and the faster the stock will shift from dealers' shelves.

I think that the Operator Level control is probably the most useful editing parameter on the DX7, although Frequency Ratio is right up there too. Adjusting this may be a 2-stage operation depending on your starting point. I'll give you the full version: press the Mode/Sync button and press the data entry buttons so that you see 'Frequency (ratio)' in the display rather than 'Fixed Freq. (Hz)', which is useful but not what we want right now. Then press Frequency Coarse and play around, remembering that you are adjusting the frequency of just one of the operators in the algorithm. If you try this and can't think of words to say, then try "Wow!". This really does give powerful control over the sound, and the Frequency Fine control goes even further. You will soon realise that if the ratio is set to a simple number like 2 or 4, then a fairly euphonious sound will result. Wander far from that simple ratio however, via the Frequency Fine control, and you will trace out a full spectrum of sounds between sweet euphony and utter cacophony. What fun! When you have the knack of editing these simple parameters you pretty much have the knack of editing the DX7. Of course, you will have to think about more complex things like how the level of the oscillators should vary in time (each operator has a level envelope), but with a bit of patience all things are possible. When you have finished editing, you'll need to save your work (and unless you have a RAM cartridge, overwrite one of the internal sounds).

Saving isn't particularly intuitive so I'll tell you how. First press Memory Protect and set the internal memory protection to off. Next, press Memory Select Internal, then hold Store while pressing the number key under which you want to store the sound.

OTHER MATTERS

The Yamaha DX7, for all its virtues, has a few vices, particularly in the MIDI department. It's a pity that this is so because as a keyboard it's very smooth and professional, with a beautifully sensitive aftertouch response. The reason I gave up my DX7 in the end was that you couldn't switch the Local MIDI off. When working with a sequencer, whatever I played on the keyboard, no matter what channel the sequencer re-channelised it to, was faithfully played by the tone generating circuitry of the DX7. This is not an adequate way of working, although the later DX7S corrected the problem. Also, the original DX7 could only transmit on MIDI Channel 1. Usually this is not a problem, but a proper keyboard really ought to be able to transmit on any channel to be considered truly usable in all circumstances. While I'm on about vices, I could remark on the fact that there are only 32 internal memories, but believe it or not this was considered to be nothing short of fantastic in those early days.

A GOOD BUY?

Yes, the DX7 is still a valuable instrument to have in your collection, particularly as secondhand prices are so reasonable. It may not have built in drum samples, sequencer or effects, but you can be sure that you are the possessor of the original classic FM sound. As an instrument in its own right it is very playable, but as I explained it has drawbacks if used as a MIDI master keyboard. The DX7S may not be quite so 'classic', but it does have MIDI Local Off and there is rather less noise in the voices.

As a final thought consider this: Roland are including in their latest drum machines classic sounds from their old revered beat boxes. Will we see a day when a synthesizer is produced (with cross-manufacturer support through a licence arrangement) that has buttons labelled 'DX7', 'D50' and 'M1' so that in one instrument you have all the classics of a bygone era. And with digital sound generation these could be accurate replicas rather than imitations. We can dream...