The Pro Soloist is a hybrid of digital and analog circuits. The internal flow of the audio signals is, in most respects, quite similar to any of our other synthesizers. That is, a raw signal (pulse or sawtooth wave) is processed through a voltage controlled filter and a voltage controlled amplifier to the output of the instrument. Two envelope generators (ADSR and AR) are available to control the VCF and VCA to determine the attack and decay characteristics of the instrument. In addition to the voltage controlled filter, there are fixed band pass filters which shape the raw waveforms for particular voices. In variable synthesizers, such as the ARP Odyssey or the ARP 2600, the signal paths, oscillator waveforms and filter characteristics are adjusted manually, In the Pro Soloist, each of these settings are programmed by a digital memory. (Read Only Memory, or R.O.M.).