A synthesizer circuit which transforms block chords into arpeggiations, under the control of the performer. (In musical terms, an arpeggiation is when a chord is played such that each note is sounded individually, rather than all at once.) In a typical circuit, the performer activates the circuit, chooses a type of arpeggiation (up, down, alternating, random, etc.) and plays a chord as a block, and the arpeggiator plays the notes in the arpeggiated sequence and continues to do so as long as the notes are held.Arpeggiator circuits originally appeared on home organs in the late-‘60s as a crutch for less capable players, but early synth pioneers such as Tangerine Dream quickly realized that they could use them to obtain sequences that would be difficult or impossible to play by hand with the same feel, and maintain these sequences over a long period while layering in other elements. An arpeggiator can be considered a primitive form of sequencer, although it is not usually described as such.