The word arpeggio (derived from the Italian arpa, “harp”) describes a manner of performing a chord. A chord is said to be “arpeggiated” when the notes belonging to the chord are performed sequentially rather than simultaneously. Arpeggios are also referred to as “broken chords.” The example below shows a C major chord in both arpeggiated (or “broken”) form and in block chord form.
Because arpeggios sound the notes of a chord in a linear rather than simultaneous fashion, they can be thought to occupy a kind of middle ground between melody and harmony, and reveal the close relationship between these two musical parameters. On the one hand, an arpeggio “melodicizes” a chord, and it is common for melodies to include or even to feature arpeggiation. On the other hand, the common use of arpeggiation in melodies also reveals the extent to which melodies express underlying harmonies.
In the context of copyright, arpeggios can thus take on an unusual status: they are one of the principal agents through which an essentially non-protectable element of music—harmony—can shade into the domain of the “original” and copyrightable.