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The Arpeggio - A Guide to Ornamentation
The Arpeggio (from Italian, Arpa)
1.
The sign 
2.
When the arpeggio is written in small notes, it still begins on the beat, but the small notes are not held down.
3.
The above rule as regards the arpeggio commencing on the beat, does not always hold good, especially when the small notes are written before the notes of a cantabile melody.
4.
The downward arpeggio is usually indicated with an arrowhead indicating the direction of the arpeggio 
5.
For clarity, sometimes an arrowhead is also applied to an upward arpeggio.
6.
When (in old music) chords are marked with the word "arpeggio," all the notes of the chord should be played rapidly one after the other, both up and down several times ad lib.