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Sunday, January 21st, 2018 12:09 am

Synth Glossary

Frequency Modulation (FM):
Frequency modulation allows the output of one oscillator to drive the frequency of another oscillator. It can generate very complex sounds from very simple waveforms and is the basis of the Yamaha DX range of synthisizers and OPL range of synthesizer chips (used in Adlib and most other soundcards)....

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Source
The Moog Source is a 2-VCO, micro-processor-controlled, programmable monophonic synthesizer, with 16 memory locations, and a 3-octave, 37-note (C-C) keyboard. It features an arpeggiator and a digital sequencer with memory for two seqences of up to 64 notes. The Source was one of the first to use digital parameter access for programming, a method now commonly found in today's synthesizers, using membrane switches, a two-digit LED display and a single data knob. Both VCOs have three available waveforms (sawtooth, triangle, and pulse; with pulse width modulation) and three available octaves (32', 16', and 8'). VCO2 can be detuned at fixed intervals and it can be also synced to VCO1. The mixer section features levels for VCO1, VCO2 and Noise. The VCF (24dB/octave) has parameters for keyboard tracking (off, 1/2, and full), cutoff frequency, resonance, and contour (Moog's word for envelope) amount. There are two ADSR envelope generators, one for the VCF and one for the VCA. The envelopes can be set in single or multi trigger modes. The LFO (triangle and square waveforms) can be routed to the VCOs and the VCF. The Source also features a sample-and-hold which can be routed to the VCF. To the left of the keyboard is the pitch bend and the modulation wheel, along with two octave-switching buttons. These and a volume knob are the only dedicated controls. On the back panel are the audio out, cassette interface, a recessed pitch knob (for fine tuning), and CV and S-trigger inputs and outputs.

The 16 factory pre-sets are: Lead 1, Lead 2, Horn, Flute, Clav Bass, Vibes, String Bass, Harpsichord, Organ, Trill Voice, Taurus, Synthevox, Sax, Wind, Snare Drum, and Lead 1 (duplicated here so that if you wanted to, you could use this extra slot to move patches around). Programs are saved and loaded via a cassette interface.

"This was Moog's first programmable synthesizer. In its own way, the Source was as revolutionary in 1981 as the Minimoog was a decade earlier. Gone were the knobs and switches; gone was the subdued, school- lab design; gone was the compulsion to create your own sounds. The Source was new, and because it was new, it was expensive. Sales figures, given all factors, were Impressive."

"The Source is one few mono synths to employ digital access control in place of knobs and switches and one of not many more to offer program memories. The first is a bit of a pain, frankly, the sec- ond, welcome, provided you are not one of those purists who regard early use of microprocessors as the thin end of an invidious wedge. "First-time spotters should note the free-flowing incremental wheel that Roland later clasped to its bosom and called its own, soon to be followed by the rest of the music industry. The system, by now common as muck but then revolutionary requires you to stab a parameter "pad" and then spin the wheel to the desired parameter value, as displayed on a small screen. The technology required for the device and system was expensive, because at the time there were no off-the-shelf components within a reasonable budget.

"The first thing to strike you about a Source are its radical looks. This rethink from the typically understated classic Moog lines came from the marketing brains at Moog's then- parent company, Norlin Industries (as opposed to Moog itself, which hired a crack industrial design team for the job).

"Under this alarmingly garish hood (how the tra- ditionalist Bob Moog, by now long since parted from the company, must have gagged), lie a pair of fully independent VCOs, separately tunable and offering a choice of triangle, sawtooth and variable-pulse waves, which can be forced back together using hard sync. Pink noise is an additional sound source, with its own level control.

"As you might expect, the filtering is 24dB/oct lowpass with cutoff frequency and resonance (finally called by this name; Moog had previously stuck to "emphasis") controls, plus the full ADSR envelope generator. This made the creation of filter shapes rather more of a precision exercise than it was on earlier Moog synths. The filter can track the keyboard (fully, half or off). The LFO has sine or square waveshapes, plus a sample-and-hold feature. The amplifier too has the full ADSR collection of envelope parameters.

"Viewed today, the parameter list is full without being overly generous, and the user interface...well, fairly commonplace. In 1981, the Source was about as familiar and friendly as a cigarette machine in kindergarten. People pulled this and twirled that and nothing much seemed to happen.

"So they resorted to the 16 memories... and amused them selves with the assorted lead synth, string, organ and flute presets. The Source still cops a lair Taurus pedal, and for the terminally lazy, a second cassette of sounds was made available from Jan Hammer's programming. The presets are recallable from buttons that run along the front lip of the panel above the keyboard, sharing duties (in "Level Two" mode) with controls for a small, real-time-only sequencer and an arpeggiator. The sequencer has the neat ability to be transposed in real time simply by hitting a new key on the keyboard. The arpeggiator is fairly limited and can only be clocked internally from the LFO clock."

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