Which musical term indicates the notes of a chord played one after another, rather than all at once?
And the answer: Arpeggio.
Instead of writing three or more notes of a chord to sound at the same time, a composer writes each of the notes separately, to be played one at a time. Famous examples of the arpeggio include the beginning of Beethoven's Moonlight Sonata, and the chorus of "Ob-La-Di Ob-La-Da" by the Beatles.
The word arpeggio comes from the Italian word arpeggiare, which means "to play on a harp." This is most likely due to the fact that arpeggios are essential elements in the repertoire of harp players. Arpeggiation is especially helpful on instruments such as the harp because it allows the player to play and articulate each chord tone up and down the strings.
In some instruments, arpeggios are the primary mode of playing chord tones. Banjo players, for one, use arpeggiated forms of chords in most styles of playing, however, it can be most prominently heard in bluegrass music. In bluegrass, a banjo roll is a pattern played by the banjo that uses a repeating eighth-note arpeggio. The vast majority of bluegrass tunes are made up of these roll patterns. The patterns are often chopped and changed to suit each song, but can always ultimately be traced back to a few core ideas.
Arpeggios are not common in just bluegrass, though. Arpeggios are applicable in various music genres such as pop, European classical music, metal, rock, blues, and jazz, to name a few. However, the use of arpeggios within different styles varies widely. In jazz and blues, arpeggiation is used more frequently as a soloing technique rather than melodic accompaniment.
Listen to Beethoven’s Moonlight Sonata below to get a feel for arpeggiation in action.