You are here

Yamaha TX802

FM Synth Module (Retro) By Paul Ward
Published January 1997

Paul Ward dons a Miami Vice‑style jacket and a pair of pink‑rimmed Armani shades, and travels back to the '80s heyday of FM synthesis for a look at the one‑time flagship of Yamaha's synth range, the multitimbral TX802 expander.

Yamaha had a runaway success with FM synthesis (see the 'Classic FM' box) in the 1980s, starting with the release of the 6‑operator DX7 in 1983, and moving through a seemingly never‑ending series of both 6‑ and 4‑operator spin‑offs. The commercial success of FM synths was very much reflected in the music of the day: classic tinkly FM electric pianos, spiky 'chopper' basses and an endless supply of percussive sequence sounds were mainstays of many hits produced from the early '80s onwards.

Introducing The TX802

Released in 1987, the TX802 was, to all intents and purposes, the swan song of 'traditional' DX7‑style FM synthesis. Containing the same 6‑operator sound generation circuitry as used in the DX7IID and FD keyboards (released the same year), the TX802 module was compatible with the data of all its 6‑operator predecessors, and made a valiant effort to alleviate their shortcomings in the process. If I were to sum up the TX802 in a couple of words, the 'flexible friend' cliché instantly springs to mind. Not only will it function as eight individual two‑note polysynths ('Voices'), each with its own individual audio output, but any number of these Voices can be tied together to provide more polyphony if required, and sent to either, neither, or both of the two mix outputs. At one extreme is the capability for 8‑part multitimbral operation (with each note boasting 2‑note polyphony) and at the other extreme, the TX802 can be a single‑voice 16‑note polysynth. Any combination between these two extremes is also possible. OK, so we've all got used to the dynamically‑assignable polyphony of more modern instruments, but at the time of the TX802's release, this was about as good as things got. Happily, the system for assigning Voices is extremely easy to master.

Although a Voice's two‑note polyphony may seem quite restrictive, in practice it causes very few problems. Apart from pad chords and piano lines, most bass, melody, and typical 'sequencer' lines (you know; widdly, repetitive eighth‑ or sixteenth‑note patterns) are largely monophonic. So, assign four Voices to handling a pad, use two more to double up a fat bass line, and you still have two Voices left over for percussive marimba and log drum lines. Each musical part responds on its own MIDI channel, and emerges from its own dedicated audio output. To all intents and purposes, you are now running four DX7s in your rig!

Sounds (Of The '80S)

Once you realise that polyphony is so rarely a problem, you begin to wonder at the wastage prevalent in the mighty TX816, with its row of eight TF1s (DX7‑type modules). At one time, I was running five TX7s (the rack version of the DX7), sometimes stacking two or more together with detuning to produce killer basses or complex lead sounds. The extra 15 notes of which each module was capable were never put to use! The TX802 will produce identical results (only with less output noise) in a much more convenient package. FM sounds are typically best suited to monophonic lines in any case, since they arguably lack the 'warmth' of analogue and the subjective accuracy of modern sampled sounds. For chunky bass riffs or percussive sequences, FM really takes some beating. Simply duplicating a sound on a pair of Voices and detuning them makes for some very rich sounds, especially if the results are also panned across the stereo image.

...the TX802 was the swan song of 'traditional' DX7‑style FM synthesis.

Yamaha endowed the TX802 with 128 factory preset patch memories held in internal ROM and a pair of user RAM banks, each capable of holding 32 patches and 64 'Performances'. An optional RAM card holds a further 64 Performances and two banks of 32 patches. The factory presets obviously benefited from the years that FM had already been in service, since they are mostly excellent. And that's not to say that the ones on the original DX7 were bad, merely that expectations had moved on by then! Patches such as 'Superbass', 'Nu Marimba' and 'FullTines' really show what FM is all about at its best. But when Voice patches are combined in a TX802 Performance, things just keep getting better: there are the sort of layering and key split options previously available only on the mighty (and mightily expensive!) TX816. Personal favourites include 'Fazz Synthe‑Lead', which is big and nasty enough to look after itself in a darkened alley, and '12 String Guitar', which makes many sampled attempts sound pale and lifeless by comparison. Quirky features include 'Alternate' where linked voices play alternate incoming notes. With a selection of similar Voice patches and some clever panning it is possible to have sequence lines spinning around the speakers with ever‑changing contrasts in tone and colour.

DX7 Or TX802?

Yamaha's DX7, arguably the most famous FM synth, is rumoured to be a collectors' item in Japan these days. Whilst I usually take these 'big in Japan' stories with a healthy spoonful of translucent crystalline seasoning, I can quite imagine this being the case. The TX802 may not be as famous or as 'instant' in its appeal as the venerable DX7, but for those in the know, it is a far better instrument and runs rings around its older cousin. Having used a clutch of TX7s as my FM sound sources for more years than I care to recall, the TX802 somehow managed to slip past me until just recently, and how I wish I had made the discovery earlier! If you hanker after FM sounds, there is no finer machine in which to find them than the TX802. For those who already own one — why have you been keeping quiet about it all these years? Ah, I get it...

Classic FM? — FM Synthesis

FM (Frequency Modulation) synthesis brought a whole new breed of sounds to keyboard players — and baffled the hell out of many of them when they tried to program their own. Understanding FM synthesis at its most basic is not really very difficult; the complication comes in putting all the components together in a musically meaningful way. Here's a quick 'bluffer's guide' to some of the terms connected with FM:

    This can be thought of as a digital oscillator. In most incarnations of FM, such as that used on the DX7, the operator is only capable of producing a sine wave. The more operators you have, the more complex waveforms you can produce. The DX7 has six, whilst its budget‑conscious cousins the DX9 and DX21, for instance, have four. Each operator is capable of behaving as either a Carrier or a Modulator (see below).
    This is an operator that is responsible for producing an actual audio signal.
    This is the other kind of operator. Modulators are not responsible for producing any audio, but instead, as the name suggests, act solely as a modulation source, imparting their waveform onto a Carrier to produce a more complex harmonic content. By varying the amplitude and frequency of the modulator, the harmonic content of the resulting waveform can be dramatically changed, and by using an envelope generator to alter the modulator's amplitude and frequency, sounds can be created whose tone changes over time. It's also quite possible for a modulator to act upon another modulator — which is where the complexity and confusion usually starts! The principle of arriving at complex waveforms by adding harmonics explains why FM is referred to as a form of 'additive' synthesis.
    It is quite possible for an operator to loop its output, and effectively modulate itself. In Yamaha's incarnation of FM, this is mercifully restricted to one operator per algorithm.
    This is simply a configuration of operators, specifying which are to be carriers and which are to be modulators. By making all of the operators into carriers, you have the makings of a simple tone‑bar organ. At the other extreme, if you make only one of the operators a carrier, the remaining operators are all available to act as modulation sources, and extremely complex waveforms can be produced.

The continuing obsession with all things analogue seems to have sent FM synthesis into the wilderness between the realms of 'newest is best' and 'they don't make 'em like they used to' — FM just ain't hip. But for anyone who judges musical equipment by using their ears, rather than by the fashion pages of Hello, the value for money factor ratio of the Yamaha DX/TX range is very favourable. Forget trying to make a DX21 sound like a Minimoog — it's never going to happen. Instead, delight in the quirky metallic twangs, pings and thunks at which FM excels. Mix them in with a couple of analogue synth loops and you might just be responsible for setting off a second‑hand FM synth boom in the late '90s.