The third version of the ARP Pro Soloist was released in 1977 and was produced till the end of ARP in 1981.
The pressed keys on the keyboard were part of a matrix to generate a 6 bit binary code to select the octaves (upper two bits) and the pressed key inside an octave (4 bits). This code was then used to divide down a CV modulatable (for vibrato and pitch-bend) master top oscillator of about 150 kHz to the audio frequency of the generated pulse or a staircase formed sawtooth wave as starting point for the monophonic preset sounds:
These presets used different adjusted preset values for fundamental octave, waveshape selection (pulse/sawtooth), the pulse width, resonator preset EQ banks (ranging from 2 to 5 bands), a high pass filter, a lowpass filter and a VCA. Additionally the two envelopes (AR and ADSR type) are routed to the lowpass filter or the VCA in different combinations and amounts.
By momentary switches a logic array was set to change the presets parameters amounts and routings.
The aftertouch can be routed to several modulation destinies:
- Wow (lowpass filter cutoff frequency)
- Growl (preset filter modulation)
- Brilliance (filter resonance)
- Vibrato (amount of vibrato)
- knob for vibrato speed
- switch to turn automatic retrigger with the same speed as the vibrato on/off
- portamento on/off switch
- volume fader
- brilliance fader
- touch sensitivity fader
- portamento speed
- triple octave selection switch