Recordings from Persona Digital
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Trinity P-2500 Band
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Stephen Gislason

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Analog Synthesis 1974

I started my synthesis career in 1974 with module kits from John Simonton (PAIA). A module kit consisted of a circuit board, transistors resistors and capacitors. There was a circuit schematic and some instructions. You supplied the soldering iron and assembly skills. A basic system required 8 kits, one Voltage Controlled Oscillator, one Envelope Generator, one Voltage Controlled Amplifier, one Low Frequency Oscillator, one Noise Generator, one Low Pass filter and one Band Pass Filter. A power supply was required.

The modules had jacks on their front panels so that each could be connected to other modules by using patch cords. To generate musical sounds you connected a piano-like keyboard controller that sent out a different voltage from each key to a voltage controlled oscillator that generated the sound waves at the appropriate pitch. The oscillator was typically connected to a voltage-controlled amplifier that was in turn controlled by a ramp generator, since musical sounds emerge and decay within an amplitude envelope. To finish a convincing musical sound, many modules would be connected in a single path.

The VCO module produced sine waves, square waves and sawtooth waves. The pitch was determined by a voltage input for a keyboard, for example. The simplest synthesis path was keyboard > VCO > EG >VCA> LPF to BPF > sound amplifier.

Robert Moog created a popular analog synthesizer,  the Minimoog  (1970)  with a built-in keyboard and  internal connections set by switches. The Minimoog design  became a standard for synthesizers that followed. In the late 1970s synthesizers become portable keyboard instruments used in live performances.   The technology path lead to integrated circuits, digital  modules and complex, hidden interconnections that were programmable. Voice controllers such as  pitch and modulation wheels, expression and sustain pedals also became standard.

Synthesis Years Later

Below is an EMU diagram showing the synthesis architecture in their P2500 and X2 Emulator. The Voltage Controlled Oscillator has been replaced with sound samples which loop to produce sustained sounds. Samples are digital files. Samples playback through a bank of filters and then an amplifier with envelope and panning controls. A host of variables control each stage of sound production. Amplitude envelopes creates the attack, sustain decay characteristics of an instrument. Low frequency oscillators modulate the amplifier to create effects such as tremolo and vibrato. Filters change the timbres of sound and sweep filters create moving timbres. Filters can be controlled by knobs on the proteus; by low frequency oscillators, by the keyboard and by foot pedals.

More About EMU X2 Sampler/Synthesizer

More About EMU Proteus 2500

Persona Digital Studio is located on the Sunshine Coast, Sechelt, British Columbia, Canada. www.personadigitalstudio.com  email  music@personadigitalstudio.com. Our Music catalogue includes recorded performances by the Trinity P2500 Band, Em4U, and the Persona Classical Consort. Music downloads are available from iTunes, Napster, AmazonMP3 and from our companion website: Persona Digital.  We have enjoyed association with Reverb Nation who provides an online service for musicians to present and market their music.