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Sunday, July 22nd, 2018 10:26 pm

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)....


The Odyssey is first duophonic (ability to play two notes at the same time) synthesizer. This 37-note synthesizer was used as an educational tool in ARP's "Learning Music with Synthesizers" book. A very popular keyboard for ARP, it was almost as popular with musical groups as the Minimoog. The Odyssey was made in three versions. The first version was off-white, the second (in 1977) was black with gold markings on its front panel (see photo above). The third (1977 and later), and more common, version was black with orange markings. The third version has an external audio input, a steel frame, and "is also equipped with Proportional Pitch Control (PPC), ARP's latest contribution to more expressive synthesizer performance. The triple-pad, pressure-sensitive controller lets you bend notes sharp and flat, and add vibrato, all without moving a single slider or switch."----[from the ARP Odyssey promotional brochure courtesy of Kevin Lightner]

The PPC is basically three rubber pads underneath the keys. One to the left of the key for flattening the pitch, one in the middle for vibrato, and one to the right for sharpening the pitch. The pads were pressure gradient from back to front. If you pressed hard on the front, you get a semi-tone change, but if you press hard on the back you get up to a fifth change.

Later models have good CV/gate interface. Later Mark I's have mini-jack sockets squeezed in on the right of the back panel. Some Mark II do not come with CV/gate interface, though they do have the PPC. Mark II Odysseys have XLR outputs. Also some of the earlier models have some of their circuitry encased in resin, a trick ARP used often in their earlier years to maintain temperature stability (or as some say, to guard trade secrets). For whatever reason they did it, having their sockets enclosed in resin makes it difficult, if not imposible, to repair some units.

Both VCOs are switchable between sawtooth, square, and pulse waveforms with oscillator sync, a ring modulator, and pink or white noise. Pulse-width can be modulated manually or with the LFO or the ADSR envelope generator. There is a high-pass filter, as well as a low-pass self-oscillating VCF. The filter can be controlled by either of the two envelope generators, an ADSR (attack, decay, sustain or "delay", release) and a simple AR (attack, release) and modulated by the LFO, sample-and-hold, the keyboard, or a separate CV (pedal) input on the back panel.

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