This lack of programmability was compensated by giving the performer control over the voice expression, adding "growl", "wow", "brilliance", portamento, pitch bend, and/or vibrato to the timbre.

Although initially marketed to home organists, it found its way into the hands of such famous musicians as Tony Banks of Genesis, Josef Zawinul, Billy Preston, Vangelis, Tangerine Dream, Edgar Froese, Peter Baumann, Christopher Franke, Gary Numan (his 1980 number one album Telekon is heavily built on the Pro Soloist), Anthony Phillips (whose 1977 album The Geese and the Ghost took its name from Phillips' nicknames for two sounds produced by the Pro Soloist),[2] John Entwistle, and Steve Walsh of Kansas (particularly on the 1975 release Song for America).

It was also used by Funk keyboardist like Junie Morrison on the Ohio Players song "Funky Worm" and by Bernie Worrell in the Parliament Mothership Connection (1975) album.

Around the same time, the company released its ARP Odyssey synthesizer, a powerful duophonic instrument, as the flagship of its performance line.

The Pro Soloist is monophonic and features a multiple-trigger, low note priority, transposable 37-key three-octave keyboard with aftertouch (i.e., pressure) sensitivity.

The Pro Soloist was significant in using digital read-only memory (ROM) chips to program all of its internal signal paths.

There are four slider pots to the left of the keyboard to control volume, touch sensitivity, brilliance (VCF Cutoff), and portamento speed during live performance.

There is also a rotary pot which serves double duty to control both the rate of Vibrato or Tremolo (dependent upon preset) and Repeat, which causes the LFO to retrigger the envelopes of any selected voice upon key depression.

Once the audio signal is routed through the mixer and resonators, it passes through a low-pass filter and amplifier each under the control of an attack-release (AR) or ADSR envelope generator, or both.

A later instrument, the ARP Explorer (1974-1978),[3] was similar to the Pro Soloist, but allowed basic modification of the voices beyond the presets programmed into the memory.