A monophonic performance synthesizer manufactured by ARP Instruments. Marketed as a competitor to the Minimoog, the Odyssey became one of ARP's more popular models. The Odyssey architecture consisted of two VCOs, an LFO, a sample and hold circuit, a VCF, a mixer, and two envelope generators. The unit was packaged into a compact case with a three-octave keyboard and a large, flat and nearly square panel area. Like the 2600, nearly all of its controls consisted of ARP's characteristic slider pots and slide switches. Most of them came from the factory with color-coded rubber tips on the sliders, making for a very colorful appearance. The Odyssey first appeared in 1972 and remained in production until the company's bankruptcy in 1981.
Many revisions were made to the Odyssey during its production run, but the changes can be categorized into three generations. Curiously, there were also three distinct panel color schemes used during the production run, but the panels do not correlate exactly to the three generations; when examining an Odyssey, always look at the model number to determine the vintage. The "Mark I" Odyssey was model 2800. It is distinguished by the two-pole model 4023 VCF, and a non-spring-loaded pitch bend rotary knob at the lower left corner of the panel. Most but not all Mk I's have a white painted panel with dark gray graphics. The "Mark II" Odyssey consisted of models 2810 through 2813 (ARP began incrementing the model number for each minor revision). The major changes were the replacement of the 4023 VCF with the model 4035 four-pole VCF, and the replacement of the pitch knob with a system ARP called "Proportional Pitch Control" (PPC). The latter consisted of three pressure-sensitive pads. The left pad, when pressed, bent the frequency of the VCOs downward by an amount proportional to how hard the pad was pressed. The right pad bent the frequency upwards; the middle pad added vibrato based on the LFO settings. Additionally, control voltage and gate input jacks became standard (they had been available as a field kit for the Mark I), and the power supply was improved. Most Mark II Odysseys have a black painted panel with gold graphics.
The 4035 VCF was a copy of the Moog transistor ladder design. Users liked the sound, but Moog Music made noises about a lawsuit. This was quickly settled and ARP set about designing a replacement, which became the 4075 VCF. The "Mark III" Odyssey (model numbers 2820 through 2825) featured the 4075, and a wider case which provided better access to the notes at either end of the keyboard. The power switch was moved to the rear of the case, and lower-noise XLR outputs were added for studio use. Most examples of this model bore ARP's iconic "Halloween" paint scheme: a black panel with orange line and block graphics, and white legend text.
In the early '70s, there were some fierce Moog and ARP partisans, but both the Minimoog and the Odyssey are now regarded as fine examples of their era, and Odysseys fetch a premium on the collector market. The PPC system was always controversial; many performers hated it but some preferred it to the conventional pitch wheel. The Mark II models with the 4035 VCF seem to be the most desirable; the Mark IIIs with the 4075 filter have the same design error as the model 4072 filters in the 2600, which limits the output bandwidth. However, as in the case of the 2600, this can be fixed by changing a few resistors. Unlike the 2600, no Odysseys were manufactured with potted circuitry, and they are generally considered easy to work on.
An interesting aside: the synth circuitry of the ill-fated Avatar guitar synthesizer was essentially the same as the Mark III Odyssey. Since the Avatar has CV/gate input jacks, it can be thought of, and used as, a keyboardless Odyssey.
In 2015, Korg, working with former ARP designer David Friend re-introduced the Odyssey, re-creating nearly every detail of the Mark II including the PPC, the black/gold panel, and the ARP name and logo. As of 2017 that line has been expanded; in addition to the original "86%" model, a "FS" model is available that is the exact same size as the original Mark III and has full size keys. The FS is available in all three panel styles (all have the same circuitry and controls). In addition, these can be had as tabletop units sans keyboard.