The A-129 is a 15 band modular vocoder and the minimum requirement is the A-129/1 analysis section and the A-129/2 synthesis section, which are always supplied as a pair.
The vocoder needs two input signals, a speech element which serves as the raw material for the tonal shaping, patched into the analysis section, and a carrier signal which is patched into the instrument input of the synthesis section.
The speech signal is chopped up and analysed in the A-129/1, and then combined with the carrier signal in the A-129/2. As a result of this procedure the carrier signal assumes the tonal character of the speech signal, but maintaining it’s own pitch.
The links between the analysis and synthesis are external, using 15 patch leads (supplied). This interface can be used for additional processing, such as an attenuator or slew limiter (the A-129/3 is optimized for this).
The A129/2 can be used as a stand alone frequency selective VCA, with effective bands at 100Hz, 110Hz, 160Hz, 230Hz, 330Hz, 500Hz, 750Hz, 1.1KHz, 1.3KHz, 1.6KHz, 2.3KHz, 3.3KHz, 5KHz, 7.5KHz and 10KHz.