Ornamental note, usually a second, that is melodically connected with the
main note following it. In music before the 19th century a. were usually
performed on the beat, after that mostly before the beat. While the short
a. is performed as a short note regardless of the duration of the main note
the duration of the long a. is proportional to that of the main note.
An appoggiatura may have more notes preceding the main note.