1 Pitch
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-style orchestras these days tune to a pitch with a frequency of 440 cycles), given names (that pitch is labeled A), and collected in scales. Scales are discussed in Chapter 3.
2 Dynamics
In scientific terminology, amplitude is the level of strength of sound vibrations—more precisely, the amount of energy they contain and convey. As big guitar amplifiers attest, very small string vibrations can be amplified until the energy in the air transmitting them rattles the eardrums.
In musical terminology, the level of sound is called its dynamics. Musicians use subtle dynamic gradations from very soft to very loud, but they have never worked out a calibrated scale of dynamics, as they have for pitch. The terms used are only approximate. Like the indications for tempo, the terms used for dynamics are in Italian.
The main categories are simply loud and soft, forte (pronounced fór-teh) and piano, which may be qualified by expanding to “very loud” or “very soft” and by adding the Italian word for “medium,” mezzo (mét-so): Changes in dynamics can be sudden (subito), or they can be gradual—a soft passage swells into a loud one (crescendo, “growing”), or a powerful blare fades into quietness (decrescendo or diminuendo, “diminishing”).
3 Tone Color
At whatever pitch, and whether loud or soft, musical sounds differ in their general quality, depending on the instruments or voices that produce them. Tone color and timbre (tám-br) are the terms for this quality.
Tone color is produced in a more complex way (and a more astonishing way) than pitch and dynamics. Piano strings and other sound-producing bodies vibrate not only along their total length but also at the same time in half-lengths, quarters, eighths, and so on. The diagrams above attempt to illustrate this. Musicians call these fractional vibrations overtones. They are much lower in amplitude than the main vibrations; for this reason, we hear overtones not as distinct pitches, but somehow as part of the string’s basic or fundamental pitch. The amount and exact mixture of overtones are what give a sound its characteristic tone color. A flute has few overtones. A trumpet has many.