Arpeggio

The word comes from the Italian arpeggiare, to play on a harp. A harpist sweeping through a chord string by string makes exactly this sound.

Take the notes of a triad and play them in order. A C major arpeggio going up is C E G C; coming down it is C G E C. An A minor arpeggio is A C E A. Because the notes are the chord’s own notes, an arpeggio fits over its chord automatically, and the listener still hears the harmony even though the notes arrive one by one.

A few related names:

• Broken chord is the general term for any chord split into single notes, in any order. The classical piano pattern C G E G (lowest, highest, middle, highest) is a broken chord called Alberti bass, after the composer Domenico Alberti.
• Rolled chord is a chord spread quickly from the bottom note up so all the notes ring together, like a fast strum. Sheet music marks it with a wavy vertical line in front of the chord, and keyboard players often call it an arpeggio too.
• Arp is short for arpeggio. On synths it usually means the arpeggiator, a feature that plays the arpeggio for you, locked to the tempo, while you hold the chord.

Arpeggios turn up in guitar fingerpicking, piano accompaniment and synth leads, and students practice them to learn the shape of each chord. They also make a reliable start for a melody: take the chord tones, then add passing notes between them. How to write a melody over chords shows how.

In Gelato Chord, Arp mode plays the chord you hold as an arpeggio: up, down, up-down, down-up, random or pick, at rates from quarter notes to swung eighths, locked to the tempo.