Analog Synthesizers: Understanding, Performing, Buying

From the Legacy of Moog to Software Synthesis

Mark Jenkins

• Editorial: Routledge
• Año: 2019
• ISBN:
  9780429844379
• Edición: 2
• Categoría: Technology & Engineering
• Categoría: Acoustical Engineering

Making its first huge impact in the 1960s through the inventions of Bob Moog, the analog synthesizer sound, riding a wave of later developments in digital and software synthesis, has now become more popular than ever.

Analog Synthesizers charts the technology, instruments, designers, and musicians associated with its three major historical phases: invention in the 1960s–1970s and the music of Walter Carlos, Pink Floyd, Gary Numan, Genesis, Kraftwerk, The Human League, Tangerine Dream, and Jean-Michel Jarre; re-birth in the 1980s–1990s through techno and dance music and jazz fusion; and software synthesis. Now updated, this new edition also includes sections on the explosion from 2000 to the present day in affordable, mass market Eurorack format and other analog instruments, which has helped make the analog synthesizer sound hugely popular once again, particularly in the fields of TV and movie music.

Major artists interviewed in depth include:

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• Hans Zimmer (Golden Globe and Academy Award nominee and winner, "Gladiator" and "The Lion King")

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• Mike Oldfield (Grammy Award winner, "Tubular Bells")

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• Isao Tomita (Grammy Award nominee, "Snowflakes Are Dancing")

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• Rick Wakeman (Grammy Award nominee, Yes)

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• Tony Banks (Grammy, Ivor Novello and Brit Awards, Genesis)

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• Nick Rhodes (Grammy Award Winner, Duran Duran)

and from the worlds of TV and movie music:

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• Kyle Dixon and Michael Stein (Primetime Emmy Award, "Stranger Things")

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• Paul Haslinger (BMI Film and TV Music Awards, "Underworld")

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• Suzanne Ciani (Grammy Award Nominee, "Neverland")

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• Adam Lastiwka ("Travelers")

The book opens with a grounding in the physics of sound, instrument layout, sound creation, purchasing, and instrument repair, which will help entry level musicians as well as seasoned professionals appreciate and master the secrets of analog sound synthesis. Analog Synthesizers has a companion website featuring hundreds of examples of analog sound created using dozens of classic and modern instruments.

1
What is analog?

Before starting to look at the creative aspects of analog sound synthesis, it will be a huge help to develop a basic understanding of the principles of physics governing the whole subject of sound – perhaps because of all the methods of electronic sound creation, analog synthesis is probably the closest to those basic scientific principles. If that means a few hours thinking about what sound really is, how it can most easily be created electronically and how it is interpreted by the human ear, then that time spent will be more than paid back through a deeper, more intuitive approach to the handling of analog synthesizers, modules, and effects. So let’s briefly take a look at some very basic physics before starting to look at analog instruments themselves.

Sound

Sounds detected by the human ear only exist because of the medium of the air (sounds can also be transmitted through solid objects or liquids, but for our purposes we’re discussing sounds created electronically and ultimately reproduced by some kind of conventional speaker system). A sound is a repeated pressure wave – a more or less regular change in the pressure of air arriving at the human ear, specifically at the eardrum.

600 BC Greek philosopher Thales finds that rubbing amber (electron) makes it attract small objects

When a sound strikes the ear, it arrives in the form of a rapid series of changes in the air pressure at that point in space. The most obvious way to create such pressure waves is to move an object contained in the same air medium somewhere nearby. You could do this just by striking two pieces of wood together, but in the case of electronic sound creation, the moving object is usually the cone of a speaker, which moves because it is attached to a magnet encircled by a coil of wire through which an electrical signal is passed – this is the same principle as an electric motor, but designed to create backward and forward rather than circular motion. The electrical signal, and so the sound reproduced, will have three major parameters: frequency, amplitude, and wave shape. Each is explained in the following paragraphs.

(a, b) Representation of a sound with increasing frequency (pitch). (c, d) Representation of a sound with increasing amplitude (volume). (e, f) Representation of simple organ and piano volume envelopes, and a complex volume envelope showing attack and decay times, sustain level and release time.

Frequency

If one area of increased air pressure hits the ear each second, we call this a one cycle per second (CPS) or one hertz (1 Hz) sound, and the value in Hz of the sound is referred to as the frequency, or, in musical terms, the note or pitch of the sound. In fact, a 1 Hz sound is not audible to the human ear; sounds begin to become audible at around 20 Hz. A very low hum, such as those sometimes generated by electrical equipment, will be at 50 or 60 Hz. Low-pitched instruments, such as bass drums and bass guitars, produce sounds predominantly around 100–200 Hz; 440 Hz is often used as a tuning standard (in musical terms it is an “A” and so is also referred to as A440). Human voices and stringed instruments tend to produce pitches up to around 4000 Hz (4 kHz or 4 k); high-pitched whistles and other instruments will be producing sound up to around 12 kHz, and the highest pitches audible to the human ear are at around 16 kHz (young people manage somewhat higher). Some electronic equipment is designed to handle pitches even higher than this because there is a belief that higher pitched sounds can have a psychological effect, although

1500 William Gilbert extends Thales’ electrostatics discoveries to include sulphur and glass

1729 Stephen Grey discovers properties of electrical conductors and insulators

not consciously audible. Whether this is true or not, it is assumed that equipment that can handle pitches higher than normally necessary will be more easily capable of handling pitches within the normal range of human hearing.

There is a further musical way of referring to pitch: classical church organs create sound using resonant pipes, the length of which were measured in feet. The longest pipes (perhaps 32 ft in length) give the deepest pitch, so on many analog synthesizers the pitches produced are referred to in terms of “footage”, as 64', 32', 16', 8', 4', 2' and 1' – a range which covers six octaves or more (pitch increasing by one octave each time the footage is halved). Octaves are the musical intervals most clearly seen in the repeated pattern of the piano-style keyboard, and though the term derives from the inclusion of eight white keys per octave, in Western music there are five black keys per octave to be taken into account as well.

1790 Death of Benjamin Franklin, who experimented with Leyden jars, an early form of battery

Electronic circuits can very easily be designed to create variations in output across the whole range of human hearing and beyond, and we will briefly look at what sort of electronic circuits are used in the analog synthesizer in particular. When a speaker reproduces a sound at a given pitch, it has to be able to vibrate at that pitch, which if it is well constructed, it will readily be able to do. Very small speakers are unable to vibrate at very slow speeds, though, and so the lowest pitches they can reproduce may well be relatively high; we would refer to these speakers as “lacking in bass”. Very large speakers can vibrate slowly and reproduce bass frequencies well, but may have difficulty in vibrating very quickly; the highest pitches they can reproduce may be relatively low and we would refer to them as “lacking in treble”. For this reason, speakers of different sizes are usually found in combination, to efficiently cover all the frequency ranges within the range of human hearing: usually, a small speaker (or “tweeter”) for high frequencies and a large speaker (or “woofer”) for low frequencies. Sometimes other speakers are included, designed to handle the middle frequencies (“mid-range” speakers), or the very lowest frequencies (“sub-woofers”) and the very highest frequencies (“super-tweeters”).

Amplitude

The next parameter of any electrical signal being converted into a sound is amplitude; in other words, the size of the variation in the electrical signal level, and therefore the size of the variation in the air pressure level created, or its volume. A very great change in air pressure, from very high to very low and back again, when repeated, is a loud sound; a very small change in air pressure, from high to low and back again, when repeated, is a quiet sound. Again, in electronic music we are concerned with sounds reproduced by a speaker, and the loudness literally becomes a factor of the amount of air the speaker can move. The cone in a large speaker will actually move several centimetres when in action, and can create pressure waves comprising very large quantities of air. A very small speaker may be able to vibrate at just the same speed, but since the cone is smaller, this vibration moves much smaller quantities of air and the sound is quieter.

1837 First practical electric telegraph developed in the UK by Cooke and Wheatstone

Trying to handle a very loud sound with a very small speaker can simply tear the speaker apart (it can do the same to your ears, in which the eardrum or tympanic membrane is acting like a tiny microphone, the reverse action of a speaker cone); this is even assuming that the electrical coil in the speaker can handle the very wide variation in electrical voltage represented by a very loud sound, which may simply melt the coil through excessive heating effects.

By the way, the “loudness” button found on some hi-fisystems has a related but less obvious function: it slightly boosts the highest and lowest frequencies when listening at lower volumes, to compensate for the fact that the human ear is slightly less sensitive to both of these at low listening volumes.

Wave Shape

The third major parameter of an electrical signal being converted into a sound is its wave shape. Two sounds of exactly the same pitch and exactly the same volume can sound quite different from one another. What exactly is happening here? The answer lies in the way in which the air pressure varies over time in each cycle. A regular variation that builds up towards a maximum value with its rate of increase slowing as it does so, reaches a peak, dies down to a minimum value, and then begins to build up again can be plotted against time to create a smooth repeated curve, which is referred to as a sine wave. This is the most basic type of wave, the one usually heard from an electronic tuning reference device; it is not particularly harsh or “cutting” and is often compared to the sound made by a flute or whistle.

1867 Death of Michael Faraday, who made important discoveries in the science of electricity

But it is easily possible to make an electronic circuit vary its output in a quite different way; the signal can build at a constant rate until it reaches a maximum value, then immediately begin to decrease at exactly the same rate. When plotted against time this creates a series of triangular shapes, and so is referred to as a triangle wave. This sound is noticeably different to a sine wave – somewhat sharper and more cutting, and more comparable perhaps to the sound of a bassoon.

A third way of varying a signal is for it to move almost instantaneously from a low level to a maximum level, then fall back gradually to the low level before repeating the cycle at a constant rate. Because of the series of shapes made when this is plotted against time, this is referred to as a sawtooth wave; the opposite, building up at a constant rate then dropping almost instantaneously to the lowest level, can be referred to as an inverse sawtooth wave. Like the triangle wave, both waves sound more cutting than a sine wave, but a little more nasal.

Waveforms: (a) square; (b) pulse; (c) sine; (d) sawtooth; (e) triangle; (f) noise.

A fourth way of varying the signal is to bring it up to a maximum level almost instantaneously, hold it at the high level for a time, then drop it almost instantaneously to the lowest level, hold it at that level for the same amount of time, then repeat the process. Plotted against time, this shows a series of square shapes and so is known as a square wave, and sounds stronger and more cutting than any of the previous shapes. Of course, the time for which the wave holds at its maximum value does not have to be exactly the same as the time for which it holds at its minimum value; the ratio between these two times is known as the mark/space ratio or pulse width, and can be expressed as a percentage, 20% or even 10% for “thin pulse” waves, which sound progressively thinner and weaker as the ratio decreases.

1874 Elisha Gray patents “singing telegraph”, including an elementary keyboard

One interesting technique is applicable only to the square wave and does not readily apply to other waveforms. If an electronic circuit is designed so that the pulse width can be altered, it is possible to make the sound vary from thin and weak to strong and rich at will. Doing this under the control of another circuit is referred to as pulse width modulation (PWM), a common technique for making sounds more interesting and for introducing some apparent “movement” within a sound.

Harmonics and Overtones

There is another way to look at the construction of wave shapes, involving the consideration of “harmonics”. When we consider a simple wave such as a sine wave we know its “fundamental” pitch or frequency, as discussed previously. Another wave at twice that frequency sounds naturally “in tune” with the first; we refer to it as the second harmonic and it’s musically as well as mathematically related, since it’s an octave above (another wave at half the frequency is one octave below the fundamental, and so on). A wave at three times the frequency of the fundamental can be referred to as the third harmonic, four times as the fourth harmonic and so on, and these frequencies are usually generated by musical instruments to some extent, though more quietly than the fundamental.

1876 Scots-born Alexander Graham Bell patents telephone while at Boston University

Interestingly enough, all other waves can be created from a combination of sine waves of different frequencies or harmonics superimposed on one another. To create a square wave from only sine waves, simply generate the basic frequency (the “fundamental”) plus all its odd-numbered harmonics – the third, fifth, seventh, and so on. The sine wave quickly transforms into a rounded-off square, and as more and more oddly numbered harmonics are added, becomes a more or less perfect square. The same can be done, using different combinations of harmonics, to generate the triangle, sawtooth and all other waves, and so the tone of a musical instrument or sound depends largely on its content in terms of harmonics.

Building a square wave from sine wave harmonics.

Although some advanced digital synthesizers actually work this way – this so-called “harmonic” or “additive” synthesis method was found on the Kawai K5, Korg DSS1 and a few others – in using analog synthesizers, the common wave shapes have already been created for you, and the four common simple waveforms – sine, t...