The original Yamaha DX7 was one of those instruments that transformed the music industry. First released in 1983 at a remarkably affordable price, it was the first all-digital synthesizer to be accessible to the general instrument-buying public. It supplanted the pricey, buzzy analog synths with their wall o' knobs programming interfaces and limited polyphony. The DX7 had a whopping 16 voices (the TX816 had 128!) and it seemed to be capable of simulating any instrument ever known. Forget the fact that the sound could sometimes seem a bit thin or a bit edgy - this was the sound of the '80s! For the next few years FM synthesis ruled, at least until the public began to tire of tinkling Rhodes and sparkling brass timbres, and Korg introduced the Next Big Thing in the form of the M1. Sample playback instruments in turn had their day, but their relative inflexibility left musicians hungry for direct tactile control of their sounds and a bit of the old analog grit.

We've seen the response to that need in the form of a new generation of analog modular systems, and as DSPs have become more powerful we've seen and heard digitally modeled versions of everything from the analog Minimoog to the hybrid Wave PPG. The German company Native Instruments has been at the forefront of this virtual synthesis trend, with offerings in the complementary categories of their Sampling Line, Future Line, and Vintage Line. FM7 is the latest in the latter group, joining the B4 organ and Pro-52 analog synth instruments in a rebirth that is more of a metamorphosis than a simple emulation of the classics.

Like its litter-mates, FM7 can function either as a stand-alone instrument or as a plug-in for audio workstation software. Like the others of the Vintage Line it has the look and feel of the original, but with the power of modern DSP programming and nearly twenty years of computer music evolution the new incarnation is full of many pleasant surprises. But before delving into the details, we'll first review just what FM synthesis is, and why it's a good idea to bring it back (FM mavens may wish to skip ahead).

LINEAR FREQUENCY MODULATION BASICS

The synthesis method used in the DX/TX instruments and in FM7 is called Linear Frequency Modulation. It is a synthesis technique perfected by the composer John Chowning at Stanford University and it is based on the simple modulation of one digital oscillator by another. If the modulating oscillator has a frequency lower than about 20 Hz the result is a kind of vibrato, but when the frequency of the modulator rises into the audio range it produces a number of additional frequency components. It creates a rich spectrum in a fashion that computer music programmers term "computationally inexpensive." What's more, if the modulation index is varied dynamically it can produce quite lively results.

The Yamaha implementation of Chowning's FM was to standardize the method on a group of identical synthesis elements called "operators." An operator consists of an oscillator, an envelope generator, and an amplitude scaling function that acts like an analog VCA. Operators are grouped in various combinations of series and parallel connections to form synthesis "algorithms."

VOICE ARCHITECTURE

The original DX7 keyboard and its tabletop and rack mount siblings (TX7, TX816, and TX802) had a synthesis architecture based on six operators. The "junior" models (DX11, TX81Z et al.) had only four. What's more, these operators were configured in a limited number of ways; the DX7 had just 32 possible configurations, or "algorithms." FM7 keeps the classic six operators for backward compatibility, but it adds two more special-function operators for noise/distortion and for filtering functions. The program also allows a wide-open set of configuration possibilities, and instead of just the original sine waveform it provides a choice of 32 different wave shapes!

The six Yamaha-style operators are labeled "A" through "F" and each has its own parameter editing page. These are all identical and are organized with a number of fader/numerical data input objects as well as graphic plots for envelope shape and key scaling function design. These generally follow the familiar graphic conventions first established in David Zicarelli's original DX/TX Editor, but as with many of FM7's features there is more programming power than initially meets the eye.

DX7 envelopes followed a basic ADSR (Attack, Decay, Sustain, Release) format; FM7 allows the creation of much more complex functions. Simply by Control-clicking (or Right-clicking in Windows) you can add another breakpoint to the envelope. This allows the creation of complex attack transients and decay shapes, but equally interesting is that they can also be inserted into the sustain portion of the envelope. The envelope window has a pair of vertical red lines that mark the boundaries of the sustain loop. By default this portion is a simple steady-state organ envelope, but by adding breakpoints you can reshape the looping envelope to be as complex as you like. Composers of dance music will find this especially useful for creating repeating rhythms, especially when combined with another FM7 "plus"-the ability to sync the envelope to MIDI clock (in stand-alone mode) or song Tempo (if the host application supplies this).

Operator X might well be called a "grit generator." It provides a filtered noise source (with controllable resonance) that can be mixed with oscillator-based waveforms or can serve as a primary signal source on its own. This is then routed through a wave shaping stage called a "saturator" that can provide a variety of distortion effects from soft compression up to hard clipping.

Operator Z houses a very welcome, and a very flexible filter section. A pair of 12 dB/octave multimode filters can be configured in any combination of series or parallel signal flow. This allows such effects as a classic Moog 24 dB/oct resonant lowpass filter or a vocalic resonator with two formants. As is the case with many FM7 voice parameters, the cutoff frequency can be modulated by a wide selection of control sources.

In addition to the eight operators, each voice has an Effect section with a selection of a dozen delay-based effects that range from simple chorus to "pseudo reverb." The effects are programmable per voice.

MODULATION AND CONTROL

Each voice has a number of control sources that may be linked to various parameters. Each of the eight operators has its own envelope generator, and each voice has two LFOs and a pitch envelope. A wide range of MIDI messages (note number, velocity, aftertouch, pitch bend, etc.) can control a large number of voice parameters (operator output, pitch and amplitude modulation, etc.) as was traditionally the case with the hardware versions. These are easily patched in a Modulation Matrix windows. FM7 expands upon this by allowing almost any parameter to be controlled by a MIDI message.

The MIDI Learn function can turn any MIDI fader box into a hardware programming interface or a real-time tactile performance controller. The control connections can be set up by clicking on the "Learn" button, selecting the parameter to be assigned, and then by sending the desired MIDI control message. Once such a control profile has been created, it can be saved to disk and reloaded as needed. The program comes with a set of these all ready to go.

For ease of programming (in the stand-alone version only), the computer's QWERTY keyboard can be used to play notes chromatically (and polyphonically) over a two octave range. Other keys can be used for navigation, e.g. "+" and "-" increment and decrement through the voice library while you are in any of the programming pages, and the arrow keys can step, spreadsheet-style, through all 128 programs when the library page is active. The Delete key toggles between the last two active windows, and the "0" key toggles sound off and on.

Up to eight "instances" of the FM7 instrument can run at the same time, though the maximum voice polyphony will be shared among them. This allows for eight-part multitimbral performance, or you could choose to build "stacks" by assigning different instances to the same MIDI channel. There is no particular keymapping feature, though individual operators can be limited to keyboard ranges.

LIBRARY

One instance of FM7 can hold 128 different presets, organized in a library of four blocks of 32. Individual presets, blocks, or an entire library can be saved and loaded to and from the computer disk.

In addition to its own native file formats, FM7 is able to import system exclusive data files of the "syx" format. This opens up the resources of a number of Internet download sites containing tens of thousands of DX/TX patches. Unfortunately there is no direct support for the once-popular Opcode Galaxy format. During the 1980s heyday of the DX and its kin this was the most common file format for editing and storage of patch libraries. Like many old-timers I have an enormous and painstakingly-organized collection of FM patches, and it will be a bit of a chore to convert them to .syx and ultimately to FM7 files.

METADATA

In addition to sound name, sound category, sound designer name, creation date, and an Info field that provides optional comments and suggestions such as "3 voice, ModWheel -> cutoff." These data fields are specific to the FM7's own file format, so imported "legacy" DX/TX programs won't provide any useful information, but as FM7 libraries grow this will prove useful for organizing large collections of sounds.

EASY EDIT & RANDOM MODES

FM programming can be a complicated affair, with scores of parameters to adjust. FM7 removes some of the drudgery by superimposing an Easy Edit mode on top of the low-level parameter tweaking. Parameter meta-controls such as Brightness, Harmonic, Detune, and Envelope Amount affect their individual equivalents among the operator parameters, though the relationship is relative rather than absolute. Easy parameter controls are used to "nudge" the lower level parameters either up or down in value. They can be used iteratively to zero in on the desired quality of sound, and from there the operators can be tweaked to fine tune the result.

Another quick and easy sound design tool, based perhaps on a similar function in Galaxy, is the Randomize feature in the Library window. In this case random number ranges are specified for each of several parameter categories. Repeated clicks on the "Do It!" button call up randomized combinations of parameters. This can be used to grab timbral ideas out of the ether, or they can be used to tweak existing sounds by choosing small randomization values for one or two parameters at a time.

PERFORMANCE

For most people the three main criteria for an electronic instrument are sound quality, latency, and polyphony. FM7 is quite acceptable in all three. It sounds great! While I didn't dust off my old TX802 for comparison, I was sufficiently satisfied with what I was hearing that I didn't feel a compulsion to do an A/B test for this review. Similarly I felt that latency was not an issue for me; if I played a sound with a sharp attack the result has a satisfying "snap."

The question of polyphony is less cut-and-dried because of the inescapable issue of computational resource allocation that software synthesizers always raise. When you buy a piece of dedicated hardware you a pretty well assured of a certain level of performance. A DX7 could always be counted on to have 16-voice polyphony. If you had two of them you'd have 32 voices, and so on. FM7 has a nominal upper limit of 64 voices, but your individual mileage may vary. For any computer system there is a "ceiling" on the computational demands that may be made on it, and the number of voices being played, the complexity of the synthesis algorithm, and the sampling rate being used all contribute to that load. The audio interface hardware and drivers being used also have a bearing on performance. My Digi 001 hardware delivers the music OK, but my speculation is that I might be better served by an RME or M-Audio interface.

DOCUMENTATION

The Operation Manual was written by electronic music stalwart Craig Anderton, and it displays his accustomed ability to make technically demanding concepts accessible to a range of customers. Overall the documentation is quite good, though from time to time I felt that some crucial bit of information had been skipped over. Perhaps this was because of late additions to the software that missed getting covered, but I was left with some unanswered questions and wished the manual had been more detailed and better indexed.

The 100-page text (repeated four times in English, German, French, and Spanish) is divided into basic installation, interfacing, and overview sections followed by tours of the main programming windows. It then gives a brief overview of the fundamentals of FM Synthesis and an overview of the eight operator programming pages.

For an experienced FM programmer this is probably sufficient, and it also gives enough basic information to allow the average user to tweak some existing sounds and perhaps to develop a few from scratch. However, it is not meant to be a comprehensive guide to the theory and practice of linear FM synthesis. Motivated programmers would be advised to seek out some of the existing literature on the subject, in particular the excellent "FM Theory and Applications" by John Chowning (the original patent holder on FM synthesis) and David Bristow (one of the two original sound designers for the DX7).

TECHNICAL SUPPORT

For the most part I was able to figure things out by playing with the user interface itself, and most of my questions were answered by reading the manual. By chance I clicked "NI" icon on the graphic control panel, and this launched my Web browser and brought me to the Native Instruments Web site. I discovered that there was a a maintenance update for the program, and that this fixed a few buglets that had remained in the NFR (Not For Resale) version I was using for my review. Visiting the Web site has the added benefit of a links page that connects to several DX/TX sites from which patch libraries can be downloaded.

Even with the downloadable update I had some questions of a niggling technical sort, and I decided to try out the company's telephone support. I found that I had about a 50% chance of getting right through to the very helpful support representative. The rest of the time I was given the choice of leaving a message or sitting on hold. N-I proves to have a very efficient method of encouraging customers to leave a message by requiring you to key in a response every 30 seconds. I finally did leave a message and I did indeed get a call-back from tech support later in the afternoon.

CONCLUSION

I spent a lot of time working with FM instruments in the mid-1980s and I have a strong feeling that I will be revisiting that realm quite a lot in the future. FM7 is a software synthesizer that has a lot of vitality due to its wealth of dynamically controllable parameters. It has the enormous benefit of compatibility with a huge existing sound library, and its added features open the door to the refinement and extension of existing sounds. For those who simply want to plug and play, it's ready to go. For those who want to tweak until dawn, it's ready to take you out.

BIBLIOGRAPHY

• FM Theory and Applications By J. Chowning and D. Bristow
  Yamaha Music Foundation, 1986, ISBN 4636174828 (Written for use with a DX series synthesizer, explains basic theory of FM synthesis, Bessel functions, and so on) Note: the graphs for J10 and J11 on page 176 have apparently been accidentally interchanged.
• Yamaha DX7 Digital Synthesizer by Yasuhiko Fukuda
  Amsco Publications, London/New York/Sydney/Cologne 1984 ISBN (UK) 0-7119-0653-X
• The Complete DX7 by Howard Massey
  Amsco Publications, 1986
• The Classic Yamaha DX7 by Lorenz Rychner
  Alexander Pub, 1987, ISBN 0-9390-6705-6
• Yamaha Easy DX7 : A Complete Guide to the DX Synthesizer
  Hal Leonard Pub Corp, 1986, ISBN 0-8818-8452-9
• 600 Voices for the DX7
  Amsco Publications, London/New York/Sydney/Cologne 1986 ISBN (US) 0-8256-2499-1 (UK) 0-7119-1166-5

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