You are here

Yamaha TX81Z [Retrozone]

FM Synthesizer Module By Paul Sellars
Published October 1999

Yamaha TX81Z

Paul Sellars goes back to a time when minimalism ruled in synth design...

Nowadays every synth designer knows what we want. We want knobs. We want sliders. We want retro cool, and virtual analogue modelling algorithms. We want synths that contain more cutting‑edge technology than the space shuttle, but which look and sound like they were built in 1969, by a man with third‑degree soldering‑iron burns and an unhealthy interest in ring modulation.

But perhaps the tide is starting to turn. Aren't you getting a little tired of intuitive synths, with clearly labelled knobs for every function?

No. Of course you aren't. And the Yamaha TX81Z is a prime example of many of the reasons why not — because in some ways it represents everything that was bad about synth design in the 1980s. It's obscure, awkward, unpredictable and extremely difficult to program. Now, don't get me wrong: I actually love my TX81Z and, although I don't use it in every tune I write, it will always have a special place in my heart, and on top of my Akai. Nevertheless, even the most ardent admirer of this inscrutable black box would have to admit that its design does it no favours — and that, for all its good points, it will never be considered one of the synth world's timeless classics. But before I get too carried away with my own opinions, let us examine the facts in this case...

Black And White

Yamaha's TX81Z first went on sale in 1987, and had a recommended retail price of £449. It was reviewed in the May '87 issue of Sound On Sound (as was Roland's classic D50). It describes itself as an 'FM Tone Generator' and occupies just 1U of rack space. The TX81Z's front panel is taken up with a power on/off switch, a 16‑character, 2‑row backlit LCD display, 11 buttons, and a headphone socket. The rear panel is home to MIDI In, Out and Thru sockets, two audio outputs and an unusual eight‑pin socket used for connecting a cassette recorder to load and save patch data.

In 'Single' mode the TX81Z acts as a single, eight‑note‑polyphonic instrument. In 'Performance' mode it can be up to eight‑part multitimbral, although polyphony is still limited to eight notes. In other words, if you want to use eight different sounds at once, each one will have to be monophonic. However, polyphony is assignable, not fixed. So, you could use one four‑note polyphonic voice, together with one‑two note polyphonic voice and two monophonic voices. Or you could use two three‑note polyphonic voices and one two‑note polyphonic voice — or indeed any other permutation that you can think of.

There are 128 preset patches, and 32 memory slots are provided for storing user patches. There are also 24 memory slots in which Performance data — ie. settings for volume, polyphony, MIDI channel, and so on for each of the selected voices that make up a 'Performance' — can be stored.

Other features worth mentioning are the effects, which include a 'Pseudo reverb' (which adds a kind of long release envelope to a sound), delays and pitch‑shifting delays, and auto‑panning between the two outputs. Some more esoteric possibilities include 'Alternate Voice Assign' which lets you play a different voice with every successive note, the option to tune voices to non‑standard 'microtonal' scales, and the invaluable facility of choosing a greeting message for the TX81Z to display when it's switched on!

Yamaha TX81Z rear panel.Yamaha TX81Z rear panel.

Theory And Practice

The TX81Z is a four‑operator FM synth, a distant relative of the DX7 and the direct successor of Yamaha's earlier four‑operator FM synths, such as the DX21, DX27 and DX100. The 'FM', of course, stands for Frequency Modulation — the method of synthesis that almost all of Yamaha's synths relied on for the best part of a decade. A full explanation of how FM works would take up several pages (see 'Synth School' in SOS September 1997 for just that). Basically what you need to know is that FM synthesis is very different from the 'subtractive' synthesis found in analogue synths and sample‑based machines. Subtractive synthesis basically involves passing signals through different kinds of filters to create variations in the sound. FM, on the other hand, does not use filters at all.

At its simplest, Frequency Modulation synthesis is a technique for creating complex waveforms from two sine waves. One of these is called the 'carrier' and the other is called the 'modulator'. The carrier behaves in the same way as an oscillator in an analogue synth would — it produces an audible signal. The modulator, on the other hand, does not produce an audible signal of its own. Instead, the output of modulator is used to vary ('modulate') the frequency of the carrier, creating a more complex waveform (and, hopefully, a more interesting sound) to be produced. The more carriers and modulators you have interacting with each other, the more complex the waveforms you can produce. In Yamaha FM synths, the effect that each carrier or modulator has on a sound throughout its duration can be altered by a dedicated envelope generator. Yamaha refers to this package of a carrier or a modulator plus an envelope generator as an 'Operator'. With me so far?

Yamaha's now‑legendary DX7 made use of six operators, each based upon a sine‑wave oscillator. The TX81Z is different: it has only four operators per voice, but each of these offers a choice of eight different waveforms. These eight waveforms include the basic sine wave, and seven variations created by adding additional harmonics to the pure waveform. This means that some already quite complex waveforms are available as building blocks when creating sounds, which opens up possibilities unavailable in earlier FM synths.

Programming And Sounds

However, the TX81Z's presets, whilst by no means bad, really don't do much to give you a sense of unknown territory being explored. Many of the sounds will probably seem quite familiar to DX27 or DX100 owners — and in fact, the internal architecture of the TX81Z is similar enough to those of its predecessors for it to be able to load DX27/DX100 patch data. And the kinds of sounds that made the DXs popular are much the same as the ones that may endear the TX81Z to you: namely solid, Detroit‑flavoured basses, comically rude organs and impossibly shiny electric pianos. Other usable and addictive presets include D20 'Whistling' (instant X‑Files spookiness), D27 'Noise Shot' (harsh, industrial tuned percussion) and B21 'HiString 1'.

The manual claims that "Voices and all memory parameters can be edited from the front panel. No separate programming device or computer is necessary." This is not, strictly speaking, a lie, but it is, in my opinion, debatable. It's true enough that all parameters can be adjusted using only the buttons on the front panel, but it would be misleading to suggest that editing patches on the TX81Z is in anyway easy or straightforward. This is partly due to the slightly obscure nature of FM synthesis itself, and partly because of the way this particular machine is laid out. The LCD screen is really far too small for all the information it needs to display, and consequently everything is abbreviated almost to the point of meaninglessness. Several of the buttons also have multiple functions, depending on which one of the dozens of possible edit pages you happen to be looking at, which doesn't help.

Nevertheless, I would encourage all TX81Z users to be patient, and keep experimenting with altering presets and creating new patches: the results can be well worth the effort. It's possible to subtly tweak existing voices and come up with some great patches that have both the 'classic' characteristics of the well‑known sounds, and some distinctive hallmarks of originality. You can also create some very surprising sounds — particularly twisted 'FX' noises — by starting from an initialised patch and pushing a few randomly‑chosen parameters to extremes.

Whatever you set out to achieve, however, it would be worth getting yourself a good patch editor for your computer, as the addition of a well‑designed graphical front end for the TX81Z makes it so much easier to use. You could also benefit from doing a bit of in‑depth reading about FM in theory and practice. An Internet connection can be a big help here, as there are many patch editors and librarians, and some good tutorials to be found online. There are also plenty of 'third‑party' patches to download and inspect, and this can be a great way to learn how other people program their synths.

Obscurity Knocks?

Spice Girls producer Eliot Kennedy says he uses his TX81Z for just one sound, a slightly tweaked version of preset patch C15 'Lately Bass'. In September 1997 he told SOS "'s fantastic — a classic dancefloor bass sound. It's like one of those bass sounds that Babyface uses."

Other than that, it's quite difficult to name anyone who's famous for using the TX81Z. To be fair to it, it's not really the kind of synth that is going to be anybody's 'mainstay'. Its quirky character and unhelpful front end ensure that it will never be the hub around which an entire studio revolves.

However, I think you can be pretty sure that you have heard one at work on at least one good dance track in the last year. Maybe you didn't realise, perhaps you thought it was a DX100 or a DX27, but it's quite possible that that solid, plunky bass or disturbingly cheesy organ was really the result of many hours of button‑pushing, head‑scratching and swearing in front of a TX81Z.

Buying A TX81Z

TX81Zs quite often crop up on the second‑hand market, and prices seem to vary between £80 and £150, depending on their condition. An absolutely mint example would be boxed, and still have its original cable for backing up data to cassette — although, in view of the number of patch librarian programs available for all the major computer platforms, it is debatable how useful this would actually be! You should think very carefully before buying a TX81Z without a manual, as many of the abbreviations that appear in that cramped LCD are far from self‑explanatory.

Also, patch memories are backed up by an internal battery, which the manual claims will need replacing every five years. However, my TX81Z appears to have its original battery, and still remembers everything I tell it. Once again, if you get yourself a good patch librarian for your computer, it is debatable whether or not a working battery would be essential — however, it's one more factor you can take into account when negotiating a fair price.