Harmony refers again to the “vertical” sounds of pitches in music, which suggests pitches that are performed or sung together on the same time to create a chord. Usually, this implies the notes are performed at the similar time, though concord can also be implied by a melody that outlines a harmonic construction (i.e., by using melody notes which might be played one after the opposite, outlining the notes of a chord). Simple classical items and a lot of pop and traditional music songs are written so that every one the music is in a single key. More complicated Classical, pop, and conventional music songs and items might have two keys . Classical music from the Romantic era (written from about 1820–1900) typically incorporates a quantity of keys, as does jazz, especially Bebop jazz from the Nineteen Forties, in which the key or “house observe” of a track may change …