Measure of What?

Thus far we have discussed beats as footsteps, and between‑the‑beat notes as between‑the‑footsteps banging ganglies. But there are other rhythmic features of music that occur at the scale of multiple beats. In particular, music rarely treats each and every beat as equal. Some beats are special. In ¾ time, for example, every third beat gets a little emphasis, and in 4/4 time every fourth beat gets an emphasis. This is the source of the measure in music, where the first beat in each measure gets the greatest emphasis. (And there are additional patterns: in 4/4 time, for instance, the third beat gets a little extra oomph, too, roughly half that of the first.) If you keep the notes of a piece of music the same, but modify which beats are emphasized, the song can often sound nearly unrecognizable. For example, here is “Twinkle, Twinkle Little Star,” but with some unusual syllables emphasized to help you sing it in ¾ time rather than the appropriate 4/4 time. “TWI‑nkle, twi‑NKLE , lit‑tle STAR, <silent beat>, how Iwon‑der WHATyou are.” As you can see, it is very challenging to even get yourself to sing it in the wrong time signature. And when you eventually manage to do it, it is a quite different song from the original.

Why should a difference in the pattern of emphasis on beats make such a huge difference in the way music sounds to us? With the movement theory of music in hand, the question becomes: does a difference in the pattern of emphasis of a mover’s footsteps make a big difference in the meaning of the underlying behavior? For example, is a mover with a ¾ time gait signature probably doing a different behavior than a mover with a 4/4 time gait signature?

The answer is, “Of course.” A different pattern in footstep emphasis means the mover is shifting his body weight in a different pattern. The ¾ time mover has an emphasis on every third step, and thus alternates which foot gets the greater emphasis. The 4/4 time mover, on the other hand, has emphasis on every other step, with extra emphasis on every fourth step. These are the gait sounds of distinct behaviors. Real movements by people may not stay within a single time signature for prolonged periods, as music often does, but, instead, change more dynamically as the mover runs, spins, and goes up for a layup. Time‑signature differences in movement imply differences in behavior, and so we expect that our auditory system is sensitive to these time signatures . . . and that music may have come to harness this sensitivity, explaining why time signature matters in music.

And notice that when we hear music with a time signature, we want to move consistently not only with the beat and the temporal pattern of notes, but also with the time signature. People could waltz to music with a 4/4 time signature, but it just does not feel right. People not only want to step to the beat, (something we discussed early in Chapter 4); they want to step extra hard on the emphasized beat.

This and the previous Encore section concerned rhythm. The upcoming two also concern rhythm, and how it interacts with melody and with loudness, respectively.