All music has shape. A tune “played” by a computer compared with a performance by a great violinist is as different as a poem “spoken” by a computer compared with a recitation by a leading actor. The violinist and the actor bring out the shape of the tune and the meaning of the words by subtle variations of emphasis and pace.

All music needs to be shaped in varying degrees, depending on its period and style. In the Baroque and Classical periods, composers expected a consistent pace, and performers wouldn't generally take liberties with tempi. Many Baroque tunes are accompanied by “motor rhythms,” quick or slow repeated notes that give a solid rhythmic backbone. But motor rhythms can be played with shape and direction or in a square way that bogs the music down. Without making free with the actual tempi, you can play them in a way that progresses or relaxes. If a tune is aiming at a particular note, the accompaniment needs to aim at that same spot.

Melodies need variation in emphasis and can be ruined by “bumps” in the wrong places, especially at barlines. Try singing the opening phrase of Handel's “I Know That My Redeemer Liveth” (shown on p. 178), putting an accent on every barline. Then sing it again with absolutely no emphasis on any note. You'll realize that you've been unmusical twice, because you haven't given shape to the melody.