What's the difference between i.e. and e.g.?
(from Italian appoggiare, "to lean"), in music, an ornamental note of long or short duration that temporarily displaces, and subsequently resolves into, a main note, usually by stepwise motion. During the Renaissance and early Baroque, the appoggiatura was of moderate length, averaging one-third of the main note, and was more in the nature of a melodic than a harmonic ornament. By the time of Johann Sebastian Bach (1685-1750), appoggiaturas were divided into two species: the short, which borrows an inconsiderable length from its main note and therefore has little effect on the harmony; and the long, which takes half or more of the length of its main note and therefore substantially affects the harmony, creating a dissonance that then resolves, on the main note, to a consonance. Because its purpose was mainly expressive, whether in purely melodic or harmonic terms, the typical appoggiatura in 17th- and 18th-century music occurred on the beat, rather than before it, "leaning" on the principal note, as suggested by the term's derivation