FM Synthesis: DX7

FM synthesis was not only an outstanding method for experimental music but landed a major commercial success. Although there are many more popular and valuable synthesizers from the 80s, no other device shaped the sound of pop music in that era like the DX7 did. It was not the first ever, but the first affordable FM-capable synth and can generate a wide variety of sounds -- bass, leads, pads, strings, ... -- with extensive (but complicated) editing opportunities. It was also the breakthrough of digital sound synthesis, using the full potential with MIDI.

/images/Sound_Synthesis/modulation/yamaha_dx7_angle2.jpg
[Fig.1] Yamaha DX7.

Specs

  • released in 1983
  • 16 Voices Polyphony
  • 6 sine wave 'operators' per voice
  • velocity sensitive
  • aftertouch
  • LFO
  • MIDI

The DX7 in 80s Pop

Tina Turner - What's Love Got To Do With It

  • 1984
  • blues harp preset
  • starting 2:00

https://youtu.be/oGpFcHTxjZs

Laura Branigan - Self Control

  • 1984
  • the bells

https://youtu.be/WqiCQA8ROXU

Harold Faltenmeyer - Axel F

  • 1986
  • marimbas
  • starting 1:40

https://youtu.be/V4kWpi2HnPU

Kenny Loggins - Danger Zone

  • 1986
  • FM bass

https://youtu.be/siwpn14IE7E

A Comprehensive List

Find a comprenesive list of famous examples, here:

http://bobbyblues.recup.ch/yamaha_dx7/dx7_examples.html

Programming the DX7

The DX7 can be fully programmed using membrane buttons. Alternatively, Sysex messages can be used to work with external programmers, like a laptop, over MIDI. For users new to FM synthesis, it may be confusing not to find any filters. Timbre is solely controlled using the FM parameters, such as operator freuqncy ratios and modulation indices.

Algorithms

The configuration of the six operators, respectively how they are connected, is called algorithm in the Yamaha terminology. In contrast do some of its successors, the DX7 does not allow the free editing of the operator connections but provides a set of 32 pre-defined algorithms, shown in [Fig.2].

/images/Sound_Synthesis/modulation/dx7-1.jpg
[Fig.2] Yamaha DX7 manual: algorithm selection.

Envelopes

For generating sounds with evolving timbres, each operator's amplitude can be modulated with an individual ADHSR envelope, shown in [Fig.3]. Depending on the algorithm, this directly influences the modulation index and thus the overtone structure.

/images/Sound_Synthesis/modulation/dx7-2.jpg
[Fig.3] Yamaha DX7 manual: envelope editing.

Velocity

The level of each operator, and therefor modulation indices, can be programmed to depend on velocity. This allows the timbre to depend on the velocity, as in most physical instruments, which is crucial for expressive performances.



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