Early Synthesiser History
A synthesiser is a device for creating and controlling sound. Although many people associate synthesisers with “electronic” sounds, many synthesisers available on the market today are fully capable of convincing imitations of acoustic instruments. Synthesisers are used in all styles of music and indeed without them many genres of modern music simply wouldn’t exist.

Robert Moog is widely credited with inventing the first integrated keyboard synthesiser, the Minimoog in 1970. Before this historic invention, synthesisers were modular in design and required the user to implement the signal flow between the various modules themselves using patch cables. It goes without saying that these instruments were expensive, complex and not often found outside of universities or very rich musicians’ private studios.

The Minimoog was unique and revolutionary because the signal flow of the synthesiser was fixed and it featured an integrated control panel and keyboard. Pretty much any musician could coax a performance out of this synth in a few minutes.

The control panel layout of the Minimoog mirrors the signal flow of the synthesiser itself. There are three tone-generating circuits, called oscillators that create a static, harmonically rich tone when the keyboard is played. The oscillator controls are at the far left of the panel. Next comes the filter, which is used to “sculpt” the raw  sound of the oscillator by removing some harmonics and emphasising others. The filter controls are in the middle of the panel. Finally, on the far right, are the envelope controls. These shape the sound by “modulating” (changing) the amplitude and filter settings over time. Since we start with a rich, static sound and sculpt by removing harmonics this is called Subtractive Synthesis.

This simple layout of keyboard, controls and tone generating circuitry is extremely flexible and compact. Despite their age now, Minimoogs are still sought-after and fetch high prices when they occasionally appear on the market.

Synthesisers like the Minimoog from around the 70’s and into the early 80’s were mostly analogue. An easy-to-understand example of a device that utilises purely analogue electronics is a microphone. When sound waves in the air strike the diaphragm of the microphone it vibrates in a way that is proportional to the strength of the sound wave. The diaphragm is metallic and is surrounded by a magnetic field. Any movement of the diaphragm is converted into an electrical signal whose strength and frequency of fluctuations are proportional to the original vibrations in the air. A loudspeaker is the reverse - the electrical signal is applied to an electromagnet surrounding a diaphragm. This causes the diaphragm to vibrate as the magnetic field fluctuates. The movement of the diaphragm causes the air in front of the loudspeaker to move, and we perceive this as sound.

An analogue synthesiser also uses electrical voltages to generate its sounds, and as control signals. The output of the keyboard, for example, is converted into a voltage proportional to the musical frequency of the key pressed. This voltage controls the frequency output by the oscillators and consequently the pitch of the sound that we hear from the amplifier. In synthesiser terminology, this is a voltage-controlled-oscillator or VCO for short. The Minimoog design also contains a Voltage Controlled Filter (VCF) and a Voltage Controlled Amplifier (VCA).

The voltage-controlled analogue synthesiser is pretty much a design classic and subtractive synthesis is still extremely popular.  Although digital technology has largely replaced analogue, there is still a subtractive synthesis engine under the hood of many modern samplers or ROM-based audio workstations.

Digital Synthesisers
A digital synthesiser or sampler represents sound as a stream of numbers, each number representing a sample of the signal’s voltage at that time. When streamed through a device called a Digital-to-Analogue Convertor these numbers are converted back into an analogue signal that can be amplified and listened to on a speaker.

Digital electronics have the advantage that signals do not degrade as they pass through the device. Given suitable encoding and algorithms, a digital signal can be subjected to many processes and still retain a very high signal-to-noise ratio. Digital recordings can be reproduced with near-perfect technology as anyone with a CD player will already have experienced.

Many digital synthesisers use short recordings (samples) of acoustic instruments at different pitches. When a key is pressed on the keyboard the synthesiser recalls the audio data file from memory, shifts it to the correct pitch and this forms the raw sound that the filter (which is nothing more than a set of mathematical equations) and envelopes act upon. In this way digital synthesisers can be used to create more realistic emulations of acoustic than analogue synthesisers could aspire to. In the late 80’s these kind of instruments dominated the market - the Korg M1 being a particularly notable example and the first of the so-called “workstations”.

The Korg M1 and M1R workstations. Unlike an analogue synthesiser, these units were entirely digital. a 4mb on-board ROM memory chip stored samples of a variety of instruments. These samples could be fed through a crude (non-resonant) digital filter.

The main selling points of the M1 were the realism of its internal samples, the 8-track sequencer and integrated FX unit.

The Second Coming of Analogue
The dance music revolution towards the end of that decade made it much less important to have convincing acoustic emulations, however. Many musicians making these styles of music couldn’t afford brand-new equipment and picked up older, abandoned analogue synthesisers cheaply and found their own style of electronic sounds, based heavily on sweeping the filters and changing control settings in real time. Digital synthesisers of the time generally had poor user interfaces or low quality filter algorithms and sounded greatly inferior if used in this way - this had the effect of increasing the second hand price of old analogue synthesisers, many of which were not produced in great numbers, to dizzying levels.

This situation persisted pretty much until the end of the 90’s, until technology finally caught up and it was possible to create a convincing emulation of an analogue filter on a DSP (digital signal processing) chip. Synthesisers like the Access Virus and Nord Lead emerged, with analogue-style sounds and control panels.

The advances in DSP chip speeds meant that engineers could faithfully emulate many of the characteristics of an analogue synthesiser entirely within the software of units such as the Virus. Units like these are popular because they blend the analogue control surface (which encourages the real-time modification of the sound so important to modern styles of music) and the correct type of sound without the problems associated with 20-year old hardware. Old analogue synthesisers are noisy, bulky, unstable and temperamental by comparison to their digitally-modelled cousins. When you add in the still dizzying price tag and maintenance costs associated with an “analogue classic” they start to look like a much better, if still expensive, bet.

Software Synthesisers Come Into Their Own
It would seem, in the history of synthesisers, that no particular technology stays on top for very long. Whilst hardware “virtual analogue” synthesisers employing ever-faster DSP chips became popular, the humble desktop PC processor was becoming faster too.

Since the hardware VA synth is little more than a specialised computer running a software program, once computer CPU speeds reached a sufficient level it eventually meant it was possible to transfer the same sort of software program to an ordinary PC. Due to processor speed limitations, early software synthesisers were less than impressive, much the same as their digital hardware counterparts in the 80’s.

Software synthesisers were originally stand-alone programs, with their own MIDI input for performance information, and output their audio directly via the sound card. When computer sequencers started to gain audio features it was difficult to run software synths and sequencers in harmony without multiple sound cards.

The problem was eventually solved with Steinberg’s Virtual Studio Technology (or VST for short). VST allows software programmers to create DSP “plug ins” that process or generate sound directly inside the host sequencer program’s virtual mixer. The sequencer then sends the final output from its virtual mixer directly to the sound card.

There are many advantages to using software synthesisers instead of their hardware counterparts. A correctly designed software synth has a very low noise floor (a Muon plugin typical has a noise floor beyond -96dB!). Secondly, there is no space requirement - many musicians are finding that they can squeeze their entire studio into a Powerbook and hit the road - carrying around equivalent technology in hardware form would almost certainly require a truck! The third, and maybe most powerful advantage of using a virtual studio is total recall. Host programs like Cubase and Logic automatically store all synth patches, mixer settings, FX programs directly within the song file. When you reload the song to work on it again, you’re exactly where you left off. With traditional hardware this is simply impossible. The final argument in favour of software synthesis is financial. It is much, much cheaper to equip a studio with software-based sound sources than hardware.

With processor speeds now beyond 2ghz, sequencers, software synthesis and plugins are mature technologies. Musicians working at home or in professional studios can employ these technologies at low cost to access high quality sound sources and FX processors directly within their recording environment.

Software synthesis and VST technology means no cables, no background noise, no bulk, total recall AND its easier on the wallet - It has never been a better time to be a musician!

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