The scientific term for the rate of sound vibration is frequency. On the level of perception, our ears respond differently to sounds of high and low frequencies, and to very fine gradations in between. Indeed, people speak about “high” and “low” sounds quite unselfconsciously, as though they know that the latter actually have a low frequency — relatively few cycles — and the former a high frequency.
The musical term for this quality of sound, which is recognized so instinctively, is pitch. Low pitches (low frequencies) result from long vibrating elements, high pitches from short ones — a trombone sounds lower than a flute.
Noises, with their complex, unfocused vibrations, do not have pitch. Your college chorus divides up high and low pitches among four different groups of voices: sopranos (high females), altos (low females), tenors (high males), and basses (low males).
The totality of musical sounds serves as a kind of quarry from which musicians of every age and every society carve the exact building blocks they want for their music. We hear this totality in the sliding scale of a siren, starting low and going higher and higher. But musicians never (or virtually never) use the full range of pitches. Instead they select a limited number of fixed pitches from the sound continuum. These pitches are calibrated scientifically (European-