The beginnings-a little history.
Bob Moog unveiled the Minimoog in 1970, marking the first real milestone
in the history of synthesizers. Designed to be simple enough for musicians to
play on stage, the Minimoog (see below) had the added benefit of bearing the synthesizer pioneer’s name.
It wasn’t the first of the breed. Mammoth Moog modular systems requiring musicians to connect modules with patch cords merely to create a single sound predated it. The hassle of taming these beasts proved too much for all but a few musicians and bands, among them ’70s-era sonic adventurers Keith Emerson, Walter (nee Wendy) Carlos, Tangerine Dream, and Klaus Schulze.
The Minimoog wasn’t even the first pre-wired, compact synthesizer. The EMS VCS 3, and was used by artists such as Hawkwind, Jean Michell Jarre, and Brian Eno, and preceded it in 1969. However the first models had no keyboard, and very unstable VCO’s. Great for sound effects though!
The Minimoog’s basic design provides the template for the classic
synthesizer. It sported three VCOs with one doing double duty as a modulating LFO, a mixer section, a low-pass filter with resonance, and two
envelope generators, one for the filter and one for amplifier).
Competition soon brought variations on the theme on to the scene.
ARP released the Odyssey in 1972, adding oscillator synchronization, sample and hold, and a high-pass filter to the mix (don’t worry if this is all technical babble at present, I’ll explain these things later.
The semi-modular ARP 2600 followed in 1971. Though portable and pre-wired, it still offered some external cable connections.
The basics of a Synthesizer.
Subtractive synthesis is one of the most basic, and oldest approaches to synthesizing sounds electronically.
I’ll explain some of the key phrases here:
Voltage Controlled Oscillator (VCO), this produces our sound, the pitch of which is controlled by a voltage from the keyboard. It can be a simple pure sine wave with no harmonics, or a very rich sawtooth signal.
White/Pink Noise Generator, This produces a random audio signal producing a hissing noise useful for creating percussion, the sound of wind and rain, or “breath” effects for creating certain instruments.
Voltage Controlled Filter (VCF), usually a low pass filter, this takes our sound from the VCO and filters it removing some of the higher frequencies from our audio. We can control the cut-off point for control over the timbre, and add some feedback to produce a more resonant sound. See the diagram below, that little peak at the cut-off frequency is where the resonance occurs.
The chart above shows the frequency to output level of a low pass filter, a high pass filter does the reverse- it attenuates the low frequencies and passes the high frequencies.
Voltage Controlled Amplifier (VCA), this does just what it says on the tin and controls the loudness of the sound leaving our synthesizer.
Envelope Generator (EG, also ADSR), OK so this might be a little confusing… why is the EG also ADSR? Well it generates a voltage which can be used to control both the VCF (sweep the cut-off frequency) and the VCA (the loudness of the audio).
Notice the shape of the envelope in the diagram below, it has four stages; 1) Attack (A), 2) Decay (D), 3) Sustain (S), Release (R).
The two terms are used interchangeably. However some early synthesizers just had Attack and Release controls, there was no decay control or control over sustain level.
We can control each of these sections in the following way;
1) Attack time – how fast the voltage rises to the peak.
2) Decay time – how fast the voltage drops to the sustain level.
3) Sustain level – the voltage that the mid portion of the envelope is held at, how long this is held is controlled by how long the key(s) on the keyboard are held down for.
4) Release time – how long it takes for the sustain voltage to fade to zero after the key is released.
How the different Synthesizer modules fit together.
We start off with one or more voltage controlled oscillators (VCO) with a harmonically rich sound. Harmonics being the odd or even multiples of the oscillator’s frequency. Two or three oscillators can be mixed together in the mixer along with white or pink noise if required (a hissing sound).
The LFO is just a lower frequency version of a VCO that can be controlled manually to produce tremolo, vibrato or filter sweep effects.
We then use a voltage controlled filter (VCF) using the resulting audio to boost and or cut certain frequencies. Various other methods of adding harmonics can be used before filtering such as wave-shapers, clippers and ring modulators (more about these later). The filters cut-off frequency can be modulated to provide some harmonic variation, followed by a voltage controlled amplifier modulated by an envelope wave form (ADSR) triggered by the keyboard. ADSR can also be used to modulate the VCF.
Using voltage control of pitch, timbre and amplitude gives so us a huge amount of flexibility and musicality in the instrument.
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