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Yamaha TX81Z FM Expander

This latest four operator FM tone generator takes over where the stop-gap FB01 left off. It may be fully programmable and share some of the new facilities of the DX7 MkII, but is it a winner? Mark Badger finds out.

For many synthesists, Yamaha's FB01 seemed the ideal way of gaining access to FM sounds without too much investment, but the lack of editing facilities limited its ultimate usefulness. The TX81Z avoids the same trap by offering complete programmability and a wider range of features. Mark Badger investigates...

1986 saw the widespread acceptance by musicians of the potential inherent in MIDI for both composition and performance. This increased awareness has fostered the need for quality, low cost, and highly configurable MIDI sound production units.

'Quality', because musicians want to enjoy all the benefits to be gained from transferring their compositions direct to master. 'Low cost', because purchasing a second synth is an expensive business for an already strained purse. 'Highly configurable', because both manufacturers and users have interpreted the MIDI specification individually, with the minimum of common denominators.

Seeing the potential of their FB01 to fulfill this need, and recognising why it isn't quite up to the job, Yamaha have further developed the ideas behind it.

The latest TX represents a few new departures for them, new facilities for the user, and brings us ever closer to the pot at the end of the MIDI rainbow - a versatile orchestra in a compact box (ready and willing to work any time we are!).

While continuing to utilise FM sound synthesis (as in the rest of the DX synth range) to actually create the sounds, Yamaha have acknowledged their previous faux pas by making the TX81Z fully programmable. They have also added new parameters, alternative scales, and built-in effects, and housed it all in a black, single unit high, 19" rack-mount box.


The front facia sports a 32-character backlit LCD (Liquid Crystal Display), 12 'proper' buttons, and a headphones socket. The yellow characters in the display are bright and easily readable at all angles, except from below (a common problem). As in the SPX-90 and REV-7, the four 'mode' buttons contain nifty little red LEDs to show when they've been selected. These switch the display and user through the various editing options available.

The other buttons control power on/off, Parameter Scroll (left and right, the screen isn't wide enough to show all the like parameters!), Data Entry (yes/+, no/-), and Cursor Control/Master Volume (left/down and right/up).

On the rear of the TX81Z are two audio outputs; MIDI In, Out and Thru sockets; a cassette save/load DIN socket (Yamaha supply the required DIN plug-to-minijacks lead to interface with the Line In/Out sockets of any standard cassette recorder); and a conventional mains lead - no need to mess with an external power supply.


To get straight to the nitty gritty, it sounds great! Unfortunately, it's almost as tedious to programme as all the other gizmos which interface with their users via a few buttons and a little screen (though at least it's self-contained programming wise, a drawback of the FB01). This tedium is well rewarded by the results achieved, however, and Yamaha must have done their research well as I found the parameters I wished to change most often were usually only a few button pushes away.

128 ROM (Read Only Memory) preset sounds are available for instant audition and there are 32 RAM (Random Access Memory) locations for storing your own sounds. The presets are superb - 'ElecBass 1' and 'Thump Pno' (Yamaha's names) provide an excellent rhythm and bass section; 'Java Jive' has earned a place in my heart, and I've had an extraordinary latin success with 'MalibuNite'.

Sounds are a subjective thing, so you'll have to take a listen to convince yourself. In Japan, Yamaha has a reputation for test-marketing its preset sounds to thousands of musicians before releasing its products - witness the success of the DX7 (how far would it have got if it had come out of the box with two banks of initialised RAM memory?).

Like the FB01, the sounds are supplemented by 24 Performance Memories where up to eight separate voices can be configured to respond multitimbrally and with a variety of individual parameters, such as MIDI channel, volume and tuning.


Space limitations preclude a complete description of FM sound synthesis. In short, FM works by pasting a number of waveforms on top of each other, each wave having a range of parameters which affect it. In its simplest form this involves two sine wave sources, one of which 'carries' the other. In the TX81Z there are four wave sources, or operators (as in the FB01 and DX21/27/100), and there are eight different arrangements (algorithms) of these operators, one of which is utilised for the production of each sound.

The TX81Z breaks new ground for Yamaha in that seven wave shapes other than sine can be chosen for each operator (previously their FM synths offered only sine waves for sound construction). This goes someway towards making up for the lack of operators (the DX7/TX7 both have six) and provides new frontiers for the sound programmer.

A quick scan through the presets reveals that Yamaha have used these new wave shapes with extreme care, most of the 'standards' (such as piano and bass) use pure sine waves, with the new shapes assigned to just one or two operators. Looking through the more esoteric presets, however, points to some of the fantastic sounds which can be created by using these more complex waveforms.

The extra wave shapes are made available to the user because the TX81Z uses a new custom chip with which to produce its tones. Presumably this is a further development of the chip used in the FB01.

Yamaha claim that the sound quality itself has been improved, through greater resolution of the EGs (Envelope Generators) which control the operators, though the unit uses the same custom DAC (Digital to Analogue Converter).

This development of established principles is reflected in the TX81Z's compatibility with voice data from Yamaha's earlier efforts in the field of four operator synths (DX21/27/100). I presume we can look forward to Mk II versions of these soon, containing the new chip.


One of the new features available from Yamaha (though not unique to the TX81Z) is support for the use of microtonal scales. There are 13 different scale ratios available, eleven of which are preset and two of which are available for custom programming by the individual user. The preset scales are:

Pure (major)
Pure (minor)
Mean tone
Vallotti & Young
1/4 Shift equal
1/4 Tone
1/8 Tone

The two user-programmable scales allow one to edit the scale over an octave or the full keyboard. Editing the octave scale reproduces multiples of that scale for each octave of the TX's range, whereas the full keyboard editing option allows one to tune each note on the keyboard individually.

While these options make the TX81Z ideal for the authentic recreation of Baroque and other styles of early music, I wonder how useful they will be to pop musicians, who cater for an audience with limited tonal acceptance, especially when used in conjunction with another manufacturer's instruments which cannot support such tunings. On the other hand, it provides an excellent short cut to controlled detuning, especially when stacked with a 'well-tempered' sound in a performance memory.


In their efforts to provide all things to all people, and as if they hadn't sewn up the case already, Yamaha have included programmable 'effects' within the TX81Z.

I nestle that word in quotes because these are not acoustic processors, like a digital reverb or a distortion pedal; rather, they utilise the electronic nature of the instrument to reproduce what sounds like the result of an effect.

There is a programmable 'reverb', which increases the decay time of the sound by slowing the release rates of all the operators. This is affected by the rates of operator 1 and so produces different effects depending on the settings of that operator. The reverb rate is considered as another parameter of the sound and is thus independently programmable for each voice.

The other effects are Delay, Pan and Chord. These differ from the 'reverb' in that they affect the whole of the TX's output. The Delay option allows the user to programme an echo effect, with a delay time of up to 1.28 seconds, and includes the option of shifting the pitch of the echoes as they repeat (up to two octaves in either direction). The feedback level is also programmable, as is the level of the effect itself, allowing a great deal of control over the strength of the results produced.

The Pan effect varies the output level of the sound between the TX81Z's two audio outputs, and can be controlled by the LFO, velocity, or the pitch of the note itself. The direction of the panning, and its depth, is also programmable.

Yamaha's designers have obviously played with a few Casio keyboards in their time since the Chord effect on the TX81Z allows the user to programme chords (up to four notes simultaneously) which can be replayed by a single keypress. (A form of harmoniser?) These chords can also be individually linked to up to 12 notes on whatever keyboard is used to play the TX81Z, giving more flexibility.

Though they cannot be said to be 'proper' effects, these facilities are nonetheless useful and allow users to utilise their 'real' effects units somewhere else in the mix.

Because the TX81Z makes use of its operating system to alter the characteristics of its response, noise figures are meaningless, as are signal-to-noise ratios. The manual states that there's 96dB of level to play with, and as this is well outside the range of most tape machines (pro or not) I think studios will find this unit extremely useful. One of the criticisms levelled at the TX/DX7 in studios is the amount of noise they produce, and Yamaha seems to have cured this problem in the TX81Z. On stage, of course, this sort of drawback is less apparent, any noise from the unit being lost in the garbage of general amplification.


Editing the functions of the TX is done within a system of 'modes' - 'main' and 'sub'. There are three sub-modes for each of the two 'main' modes; Single and Performance.

When in the Single main mode, the TX responds as an 8-note polyphonic synthesizer playing one sound on one MIDI channel. In Performance mode, the TX responds according to one of the 24 programmable performance configurations. You switch between the two main modes by pressing the appropriately named Play/Perform button and the three sub-modes are accessed by pressing the relevant option buttons - Edit/Compare, Utility, or Cursor.

The Voice Edit buffer allows full editing of all the FM parameters on the TX81Z, and is accessed by pressing the Edit/Compare button while in Single mode. Most of these parameters will be familiar to users of any of the current four operator Yamaha synths.

Apart from specifying the waveforms and the algorithm which a sound utilises, the programmer has access to over 100 other parameters which control the TX's production of each sound. You can turn individual operators on and off, edit the 4-stage envelopes of each operator, set their levels and sensitivity to velocity, assign LFO effect and how this manifests itself, detune each operator, set its scaling (which gives higher notes a faster attack), and adjust the frequency of each operator as a ratio of the key pressed or as a fixed value (new for the TX).

You can also compare the results of your work on all these values with the sound you started with - useful when you get lost (though I can't wait till someone introduces an option which lets you go back a variable number of steps and compare; more often than not the sound I thought was really brilliant was the last but two or something).


Those of you familiar with Yamaha synths will know what I mean by 'Function Memories'. These include the pitch bend range, portamento time, foot controller volume, etc, and whether the voice is polyphonic or monophonic.

Well, one of the major criticisms of the original DX7 was that it had only one overall Function Memory, whereas the TX7 generously offered one for each voice. In the TX81Z these functions are considered part of each individual sound and are thus accessible in the Voice Edit mode. This is a far more sensible arrangement which means, for example, that you can programme and recall a specific pitch bend range for each individual sound you create. This could make copying these extra function parameters from one voice to another very time-consuming and boring, but to deal with this and other problems, Yamaha have thoughtfully provided another sub-mode of operation, Utility mode, more about which later!


As already discussed, the TX81Z has two main programming modes - the mode which controls the sound chip that produces the specific timbres of the tones that it generates (Single mode), and the mode which determines how the TX will respond to the MIDI commands it receives.

This second mode is called the 'Performance Memory' and there are 24 of these, each allowing a different configuration of the TX's MIDI command responses. It's here that the TX can be set up to become a multitimbral unit.

These performance memories are where the pure usefulness of the TX81Z becomes apparent. People with MIDI sequencers can reconstruct most of a band (and given a drum machine, the whole band!) with the minimum of fuss. There are up to eight 'voices' available in each performance memory, and each voice has the following parameters: the sound it will make, the number of notes it will play at once (up to eight), the MIDI channel it will respond to, the upper and lower note limits, any detune or transposition, the volume and audio output channel (I, II or both) at which it will appear, whether it will be modulated by the LFO of either the first or second voice or, indeed, the LFO setting of its own voice, and finally, the note scale the voice will use.

There are other parameters which are adjustable within a performance memory but affect the response of all the voices. These are: Normal or Alternate assignment mode, Effect select, and the name of your performance memory (up to ten alphanumeric characters).

Alternate mode is pretty wild. When selected, the TX81Z only responds to messages which are received on the MIDI channel that the first voice is assigned to. It then plays each successive note that is received with the next voice in the performance assignment. So, with all eight voices assigned to different sounds, and voice 1 set to respond to MIDI channel 2 (say), the unit will only play notes it receives on channel 2 and it will play each of the eight different sounds every eight notes. Get it?

If the effect selected is Delay or Chord, it affects only the first voice used. If the Pan effect is chosen, only those voices assigned to a single audio output will be panned. Panning only works in one direction though (L-R or R-L), which some users may find a wee bit limiting.

Any Performance set-up can be instantly recalled by sending the TX81Z the correct MIDI Program Change command. You may be thinking, "Hold on, there are 128 ROM sounds, 32 RAM sounds, and now 24 performance memories. That's 184, and there are only 128 different Program Changes in the MIDI specification!!" Well, Yamaha have cunningly included a very useful Program Change Table where any of the 128 incoming Program Change commands can be made to call up any of the 184 programs!


The aforementioned Table and many other useful functions, depending on which main mode you're in, is accessed by pressing the Utility button and stepping through the options available to you.

The Single mode utilities, for instance, give you a great deal of control over the TX's MIDI functions (Yamaha have done their best to fully implement the MIDI standard and virtually any MIDI situation can be accommodated) and the cassette save/load functions (again, virtually any eventuality can be catered for, and having a tape back-up while on tour is crucial).

Other utilities allow editing of the three built-in effects and the microtonal scale. It's also from here that you can control memory protection, initialise a voice, and recall the voice you were last editing.

The last utility lets you switch between using each successive voice's individual function memories or those of the voice you were last editing (and allows you to do the parameter copying I mentioned earlier).

The Utility options available in Performance mode are limited to initialising the Performance Memory Edit buffer or jumping you straight into the Voice Edit buffer, usually accessed by pressing Edit/Compare when in the Play mode.


The FB01 showed the way towards 'the useful MIDI soundbox' and Yamaha have developed this concept to excellent result. The four operator TX81Z even gives the TX7 a run for its money, the TX7 needing something like an E! board to keep up (rumoured to be in development!). Perhaps Yamaha have something up their sleeves for the six operator fans?

Yamaha's inclusion of so many useful little features, and the thought behind how these are provided by the TX, shows how seriously they've taken MIDI and its future. The degree to which the TX81Z can be usefully manipulated is unparallelled, and reveals the computer at its heart. At the same time, Yamaha have sought to make adjustment as easy and quick as possible, given the constraints of a few pushbuttons and a tiny display (which can even be programmed to greet you when the TX is switched on!).

Those of you on the lookout for a good sounding unit to supplement your analogue mainstay, who want something with nice FM sounds which 'plugs in and goes', should be well served here. Don't be put off by all the options as they can be all but ignored (bar choosing your MIDI channel and sound!) if this is what you're after.

Where the TX81Z will really shine, however, is in the hands of those willing to extract the maximum from its programmable potential. The sheer number of options ensures that virtually anyone using MIDI in their music will get a great deal of sound for their pound.

Finally, full credit must go to Yamaha for providing the most comprehensive details of a synthesizer's MIDI capabilities and protocols (16 pages worth!) that I've ever seen in an owner's manual. Hopefully, we can look forward to some excellent 'home-made' software for the TX81Z as all the information you need is provided.

(Computer owners please take note: the TX81Z parameters are so similar to those of its predecessors that software which allows remote parameter editing for the four operator range of DX synths will work with the TX81Z. The parameters that you can't get at are those that control the Waveform, the Frequency FIN (Ratio) and FIX mode, and the EG-EG shift. Remember also, there is no chorus or Pitch EG to alter on the TX81Z, so adjusting these will have no effect. I know Dr T is hard at work writing a new module for their 4-Op Deluxe software, running on the Atari ST, which will be fully compatible with the TX81Z, and will let you edit the performance memories. For the moment, DrT's DX Editor module works with most of the voice parameters.)

My thanks to Nick Thomas at Soho Soundhouse, who steered me in the right direction.

Recommended price: £449 inc VAT.

(Contact Details)

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Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - May 1987

Review by Mark Badger

Previous article in this issue:

> Nomad SMC 1.0 SMPTE/MIDI con...

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