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The Synthesizer

Modern pop music is inconceivable without it. But what exactly is a synthesizer, and how does it work?


The »Electronauts« festival brings true musical legends together: Manuel Göttsching invented the electronic music genre in 1984 with his album »E2-E4«; with their respective bands Portishead and Goldfrapp, Adrian Utley and Will Gregory set technical production standards, while Martyn Ware defined electropop with The Human League before anyone had an inkling that this sound would come to dominate the charts in the future. What do all the acts at this festival have in common? – The synthesizer is at the centre of their musical cosmos. Or to be more exact: synthesizers built by Buchla or Moog.

»Electronauts« Festival

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I was never worried that synthesizers would replace musicians. First of all, you have to be a musician in order to make music with a synthesizer.

Robert Moog


Synthesizers are electronic musical instruments in whose development the two inventors, Don Buchla und Robert Moog, played a decisive role. Although the instruments are technically similar, Buchla and Moog applied different construction principles. Buchla focused on modular synthesizers that could be put together as the user chose. Modular synthesizers are often highly complex instruments that can take up a lot of space and are extremely expensive.

Robert Moog, on the other hand, paid more attention to the musician and his needs: he reduced the core of his synthesizers to a minimum, added a keyboard and offered them at an affordable price. The Minimoog was born! The Minimoog was easy to operate and play, so that it soon became very popular and is still being manufactured in its original form, nearly 50 years after it first came onto the market. First used mainly in jazz, progressive rock and fusion, from the early 80s at the latest the Minimoog defined the sound of big pop productions such as Michael Jackson’s iconic »Thriller«.


Moog Minimoog

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In terms of physics, synthesizers are not dissimilar to acoustic instruments such as the violin! But unlike the violin, synthesizers produce the sound electronically, and need electricity to do so. This difference notwithstanding, the two instruments have more in common than first meets the eye. They both make use of the same physical principle: air is made to vibrate, creating a tone. The violin does this by a string being plucked or bowed, while the synthesizer has to help itself artificially: it produces a vibration by electronic means.


What the string is to the violin, the so-called oscillator is to the synthesizer. The oscillator creates a vibration electronically which, when played through a loudspeaker, produces a tone with a precisely defined pitch. So the oscillator is responsible for forming the tones that come from the synthesizer. But what does this tone sound like? Over the years, several different wave forms (= kinds of sound vibration) have become established that a synthesizer can produce. When a violin is played with a bow, on the other hand, only one form of soundwave results: the so-called sawtooth wave.

Wellenform einer Geige
Wellenform einer Geige

Nomen est omen: the wave form of a sawtooth wave resembles the teeth of a plain-toothed saw. If the oscillator of a synthesizer produces a sawtooth wave, it comes close to the sound of a stringed instrument. The fact that the synthesizer doesn’t sound anything like a violin is the result of part-tones, so-called overtones, which are produced by the wooden body of the violin, for example. Overtones are the decisive factor that distinguish the sound of a plucked violin from, for instance, that of a plucked guitar. So if you change the overtones, you can make a significant change to an instrument’s sound. This in turn means that a synthesizer could be »turned into« a guitar, after a manner of speaking.


The most important tool used to alter the sound of the oscillator’s sawtooth wave is the filter. Here, too, there are various different types of filter: the most frequently used is the low-pass filter. Once again, the name itself tells us how this filter works. The low-pass filter allows the low frequencies of a tone to »pass«, while high frequencies are cut back – similar to a coffee filter that keeps back some of the coffee powder. This cutting-back of the high frequencies (overtones) can turn a very bright sound similar to that of a stringed instrument into a very dark and muffled sound.

Vom Oszillator in den Filter
Vom Oszillator in den Filter


The length of the tone, however, is decided by the final component of the synthesizer: the filter envelope. The envelope enables us to define what the tone sounds like – in a similar fashion to the way the sound of a violin is changed by different playing techniques. The filter envelope determines whether the tone produced by the oscillator sounds soft and long, or short and clipped. Four changeable parameters of the envelope are responsible for this:

  • Attack (of the tone)
  • Decay (= declining volume of the tone)
  • Sustainment (of the tone)
  • Release (= allowing the tone to die away)
Die Hüllkurve des Filters
Die Hüllkurve des Filters

Here, too, it’s helpful to take a look at the violin and its bow in order to understand how the envelope works: the attack takes place when the player brings his bow into contact with the string(s); decay and sustainment refer to holding the tone produced by the bow; and the release is the moment when the bow is taken off the string(s). Tones of a widely differing character can be produced depending on how the violin is played, or on the setting of the synthesizer’s filter envelope.


The oscillator, the filter and the envelope represent the basic construction of a synthesizer. A construction also found in Robert Moog’s famous Minimoog. As described above, the violin illustrates to good effect why the synthesizer is not unlike an acoustic instrument in terms of the underlying physics. But a synthesizer can do a lot more: unlike the violin, it can produce not one but several wave forms; it has a filter to manipulate the sound, and various other modulation tools that enable an almost endless variety of sound options.