This listing includes the manual, foot pedal, and a case. This has been set up and it is fully functional.

The ARP Quartet is a vintage polyphonic analog synthesizer keyboard produced by ARP Instruments from 1979 to 1980.

A key piece of information about the ARP Quartet is that it is a re-badged version of the Italian-made Siel Orchestra synthesizer. ARP imported and sold the Siel Orchestra under its own name with only minor changes.

Key Features and Architecture:

• Type: Analog orchestral/ensemble synthesizer.
• Polyphony: Full polyphony (49 notes, using divide-down oscillator technology).
• Keyboard: 49 full-sized keys.
• Tone Sections (4-Part Orchestral): It features four main families of preset sounds that can be played individually or two can be layered simultaneously:
• 1. Brass (Trumpet, Trombone)
  2. Strings (Cello, Violin)
  3. Organ / Reed (Organ, Celeste)
  4. Piano (Traditional Piano, Honky Tonk)
• Sound Generation: Uses divide-down oscillators and analog filtering.
• Effects: Includes a built-in Ensemble/Chorus effect (using BBD chips) which is a signature sound of string synthesizers.

Sound Editing and Control:

The ARP Quartet is limited in its editability compared to more traditional synthesizers, as it is primarily a preset machine:

• Vibrato (LFO): Features a variable speed LFO for vibrato.
• Envelopes (EG): Separate Attack and Sustain controls for the Brass and String sections. The Piano/Reed section typically has a fixed envelope.
• Filter: The Brass section often includes a "Brilliance" control, which acts as a simple filter/tone control.
• Controls: It typically lacks modern controls like pitch/mod wheels and external control (MIDI was not available).