Exploring the Yamaha DX7 | Part One

When you think of 80s music, some of the sounds that come to mind are sparkly electric pianos, metallic basses and cheesy orchestral elements. Many of these sounds came from one synthesizer: the Yamaha DX7. It was released in 1983, and was the first digital synthesizer to have an impact on popular music. Along with its eventual spiritual successors, the Roland D-50 and Korg M1, the DX7 marked a move away from warm analog sounds, to complex digital sounds. For a producer, the DX7 meant more sonic options in one box, and more versatility in a recording studio.

The DX7 generated its sound using a new method of synthesis called FM synthesis, which allowed it to create percussive sounds, metallic sounds, and acoustic sounds such as flutes. Although released in 1983, the technology behind it was developed in 1967 by John Chowning, a professor at Stanford University. The FM technology was used in an earlier synths, such as the Synclavier I & II, and the Yamaha GS1, however these were all super expensive synths, so the DX line was Yamaha’s bid at making an affordable FM synthesizer for working musicians.

FM synthesis was complicated, especially compared to the simple monosynths and polysynths before it. Programming sounds was also cumbersome on the DX synths, involving menu diving and adjusting of numbers and ratios to create a new sound. Because of this, the DX7’s presets were used more than new sounds, so the same recognisable sounds started to crop up in pop and rock sounds from 1983 onwards. In this article I’ll explore the DX7 and other DX synths, I’ll look at how they work, and then play some songs they were used in.

The DX Family

The DX synths ranged from expensive beasts to cheap consumer models, with the DX7 sitting in the middle. Because of the DX7’s popularity, Yamaha created a lot of new models, including upgraded and module versions. The biggest differences between models are the number of operators, which are responsible for creating the sound. The DX7 had six, cheaper models had four, and more expensive models had two sets of six. Like most synths, the naming convention is as confusing as possible, so here’s the breakdown:

  • DX1 (1983): The biggest and most powerful of the DX series, features two sets of synth chips, allowing double polyphony, split voices, or layered voices. Also contains double the voice memory of the DX7, polyphonic aftertouch, and a very fancy wooden case. Only 140 were made! Its prototype was the Yamaha CSDX, which was never released.

  • DX5 (1985): A rerelease of the DX1, but without the fancy keyboard, polyphonic aftertouch or wooden sides, and at a much lower price point.

  • DX7 (1983): The most famous, and widely produced of the DX synths. 6 operators, one timbre and no effects.

  • DX9 (1983): Budget, reduced-feature version of the DX7, featuring only 4 operators, meaning less complex sounds. It also lacked velocity sensitivity, and could only hold 20 patches at a time, as opposed to the DX7’s 32 patches.

More 4-Operator Models

In 1985, Yamaha released three new DX models, all cheaper models with only 4 operators and 8-voices, as opposed to the DX7’s 6 operators and 16 voices. These essentially replaced the DX9.

  • DX21 (1985): The best of the new trio of 4-operator keyboards, included an onboard chorus effect, was multi-timbral and allowed for keyboard splitting.

  • DX27 (1985): As above, but without the layering or splitting. Yamaha also made the DX27S, which has onboard speakers.

  • DX100 (1985): Same as the DX27 but with a smaller case and mini keys, making it the portable model. Chromeo, Aphex Twin & Autechre are users of the 100.

  • DX11 (1988): The last real DX synth, still only 4 operators but its ability to use waveforms other than sine waves made it powerful. They also added some ‘quick edit’ functions, to make programming easier.

Mark II Models

In 1986, Yamaha released three new DX7 models, all upgraded versions of the original DX7. All of these Mk. II keyboards upgraded the DACs to 16-bit, which helped overcome one of the original DX7’s main shortcomings: the noisy output! They are all 6-operator synths, and all patches designed on the original DX7 work with the Mk IIs. Other improvements included double the memory (64 patches), more LFOs and nicer buttons.

  • DX7s (1986): The S stands for single, as it lacks the bi-timbrality of the following models, but still has the upgraded sound quality. Toro y Moi uses this one!

  • DX7 II D (1986): The D stands for dual, as it allows for bi-timbrality, meaning you get two voices to layer or split across the keyboard.

  • DX7 II FD (1986): The FD stands for floppy disk, which allowed for way more patch memory. Also has the bi-timbrality.

  • DX7 Centennial (1987): A limited edition with a slick new design. Super rare and the keyboard glows in the dark!

Desktop DXs

  • TX7 (1985): Desktop model without a keyboard, or immediate editing capabilities. Some editing can be done with software over MIDI, otherwise it’s a great way to get DX7 presets at a fraction of the price of the keyboard model.

  • TX81Z (1987): Rack-mounted version of the DX11.

  • DX200 (2001): Modern desktop synth with an onboard sequencer, meant to be fully programmable with software.

Offshoots

  • Reface DX (2015): Small FM synth in Yamaha’s modern Reface range. 4 operators, 12 algorithms, 8 voices.

  • Korg Volca FM (2016): Portable FM synth made by Korg, with an obvious nod to the DX7 in it’s colour scheme. Powerful with 6 operators and 32 algorithms, however only has 3 voices.

Software

  • Native Instruments FM7 / FM8 (2002): FM7 was originally a software version of the DX7, however FM8 is that and more. Can load patches from pretty much every DX synth.

  • Dexed (2015): Closely modelled on the DX engine, it’s free and can load DX patches. You can even use it as a controller to program a DX7 using the onscreen interface, and as a librarian to load and save patches.

  • Arturia DX7 V (2017): Faithfully models the DX7 and adds a ton of enhancements. Adds new waveforms, tons of modulation abilities, onboard effects, and an intuitive interface.

DX Architecture

Operating the DX

The DX synths feature a simple interface, devoid of most of the knobs, buttons, faders, lights and sliders of old analog synths. Instead, there are simply two sliders, and two sets of buttons, with the first set of buttons being used to navigate the DX7’s menu, and the second set to program the DX7. Each of the programming buttons selects a parameter, and the sliders to the left set the amount, with both values displayed on the LED screen. The numbered buttons on the right have two set of functions, with the edit / compare button selecting the edit mode, used for programming the DXs sounds, and the function button selecting the function mode, generally used for performance controls.

I’m The Operator

The Yamaha DX7 is only capable of producing sine waves; no sawtooth, triangles or square waves here! It has six oscillators, or operators as they’re called in FM synthesis, and the DX’s synth engine smashes them together in different combinations using an engine called Frequency Modulation Synthesis. Although it might seem complicated – it’s really not. You start a patch with a single sine wave, which isn’t terribly exciting, but here’s what it sounds like:

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You can modulate that sine wave, just like if you were using an LFO to modulate the oscillator pitch to create a vibrato effect. This is basic modulation, and the modulation itself is audible; you can hear the pitch rise and fall, however the basic sine shape remains intact.

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That was simple modulation using an LFO, where the LF stands for low frequency, a slow, inaudible waveform. If you speed that waveform up, you get some interesting results. At first the sound is ugly and unmusical, but once the modulating wave reaches a certain speed, it starts to sound complex and musical.

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What we’ve just heard is the fundamental idea behind frequency modulation synthesis: simply modulating one frequency with another. In FM lingo, the starting sine wave would be referred to as the carrier, and the LFO would be called the modulator

While raising the modulation speed, most of the results sounded atonal, however the modulation stopped at a point when the result was musical. This is because the modulator’s pitch reached exactly half the pitch as the carrier, and this produced a stable sound. If you modulate with the same pitch, that also sounds great. Modulating pitches that are closely related sound musical, and unrelated pitches sound more metallic and atonal. In FM synthesis, we call these ratios, so a ratio of 1 is the same pitch, and a ratio of 2 is double the pitch. Check out some more ratios and what they sound like:

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  • Ratio of 1 00:00
  • Ratio of 4 00:00
  • Ratio of 14 00:00
  • Ratio of 9.2 00:00

Adding & Subtracting

There are six operators and they can be routed together in many different combinations, with multiple carriers, multiple modulators, modulators modulating modulators, and feedback systems where a modulator can modulate itself.

There are so many routing possibilities that Yamaha decided to keep things simple and create 32 set routings, called algorithms. These set the six operators to specific routings of carriers and modulators. For example, algorithm 5, seen above, has operators 1, 3 and 5 set as carriers, which are routed to the synths output, whereas operators 2, 4 and 6 are modulators, set to modulate the carrier the lines point to. You don’t need to memorise the algorithms as the DX7 has diagrams of the algorithms on the case.

LFOs

The DX7’s LFO parameters allow you to modulate pitch (PMD) or volume (AMD) using triangle, sawtooth, square and sine waves, as well as a random sample/hold function. There is a delay function that creates a delay between the key being pressed and the modulation starting, which allows you to create some human sounding vibrato effects, much like how a singer or guitarist applies vibrato after first sustaining a note.

DXEnvelope

The envelopes in the DX synths are different from classic ADSR envelopes, but not as different as you’d think. Each of the four points has two editable parameters: rate and level, with rate controlling the time it takes the envelope to get from one point to the next, and level controlling the volume of that point. This flexibility allows for some timings not possible with analog envelope generators.

Where things get really confusing is that the rates knobs are inverted, so on the DX7 you have to take the slider down to increase the envelope times. Additionally, the release level sets the initial level too. Each operator has its own envelope, allowing for complex combinations of envelopes, and the creation of patches where the FM tone morphs over time.

Scaling

Level scaling refers to the DX’s advanced key follow functions, which allow the envelope levels to be adjusted across the keyboard. The break points sets the point to split the keyboard’s scaling. The available curves are linear (constant) and exponential (proportional), and the depth function controls the amount of variation across the keyboard. The keyboard rate scaling function controls the length of the note across the frequency spectrum, allowing for longer basses and shorter trebles, much like an acoustic instrument.

Controlling & Composing

Much of the DX7’s advertising ran with the tagline The Performance is About to Begin, and the DX is a true performance synth, featuring velocity sensitive keys, aftertouch, and a connector for an optional breath controller, allowing the player to use breath pressure to imitate wind instruments. The keys have such a nice feel that the DX7 is often used a controller for other synths, even by Nine Inch Nail’s on The Downward Spiral Tour, where Trent Reznor would destroy them at every show. The performance controls are all adjustable, and allow the performer to add a human touch to recordings.

Part Two

This is Part One of Exploring the Yamaha DX7, focusing on how to program the DX7. Click here for Part Two.

11 thoughts on “Exploring the Yamaha DX7 | Part One”

  1. Hi, my DX7 master, piano and strings cartridge seems to be faulty so I’ve lost a lot of sounds. Your article has revived my spirits – maybe I’ll be able to create some new sounds instead. Thanks. Rosey

  2. Hello! This was a really interesting article, so thank you for that! I bought my DX7 somewhere around 1985 when I was an adolescent. It went into storage a decade later and I pulled it out of its case today, August 2019. And wow – it still works! I think I might use it as a composer keyboard with GarageBand… just need to see what adaptors I will need!

    1. Good stuff! The DX7’s are still great synths, the keybeds are really nice to play and if you want to program it with more visual feedback you can used Dexed as a controller.

  3. The desktop DX7 I have is called a TX7 – typo?

    Massive fan of the whole series (owner of many) and really appreciated and enjoyed reading this

  4. Hi Reverb machine. Thank you teaching and letting us explore these things. I was wondering what patches were used in Houston’s The Greatest Love of All. Cheers

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