idiophone World music classification for instruments that produce sound from the substance of the instrument itself by being struck, blown, shaken, scraped, or rubbed. The most common Western instruments in this category belong to the percussion family. Examples include cymbals, triangle, gong, and maracas.

imitation Compositional technique in which a melodic idea is presented in one voice (or part), then restated in another while the first voice continues with new material.

In this example, the voice parts build from lowest to highest (basses, tenors, altos, sopranos), each imitating the first melodic statement.


	Example: Handel, Messiah, "Hallelujah" Chorus
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improvisation Creation of a musical composition while it is being performed, seen in Baroque ornamentation, cadenzas of concertos, jazz, and some non-Western musics. See also embellishment.

incidental music Music written to accompany dramatic works.

inflection Small alteration of the pitch by a microtonal interval. See also blue note.

instrument Mechanism that generates musical vibrations and transmits them into the air.

interlude Music played between sections of a musical or dramatic work.

intermezzo Short, lyric piece or movement, often for piano. Also a comic interlude performed between acts of an eighteenth-century opera seria.

interval Distance and relationship between two pitches.

inversion Mirror or upside-down image of a melody or pattern, found in fugues and twelve-tone compositions.

Irish harp Plucked-string instrument with about thirty strings; used to accompany Irish songs and dance music (also celtic harp).

isorhythmic motet Medieval and early Renaissance motet based on a repeating rhythmic pattern throughout one or more voices.

Italian overture Baroque overture consisting of three sections: fast-slow-fast.