Music Theory Volume 1

Pitch Part 2

The difference in frequency between two pitches is called an interval. The most basic interval is the unison, which is simply two notes of the same pitch, followed by the slightly more complex octave: pitches that are either double or half the frequency of the other. The unique characteristics of octaves gave rise to the concept of what is called pitch class, an important aspect of music theory. Pitches of the same letter name that occur in different octaves may be grouped into a single "class" by ignoring the difference in octave. For example, a high C and a low C are members of the same pitch class—the class that contains all C's. The concept of pitch class greatly aids aspects of analysis and composition.

Although pitch can be identified by specific frequency, the letter names assigned to pitches are somewhat arbitrary. For example, today most orchestras assign Concert A (the A above middle C on the piano) to the specific frequency of 440 Hz, rather than, for instance, 435HZ as it was in France in 1859. In England, that A varied between 439 and 452. These differences can have a noticeable effect on the timbre of instruments and other phenomena. Many cultures do not attempt to standardize pitch, often considering that it should be allowed to vary depending on genre, style, mood, etc. In historically informed performance of older music, tuning is often set to match the tuning used in the period when it was written. A frequency of 440 Hz was recommended as the standard pitch for Concert A in 1939, and in 1955 the International Organization for Standardization affirmed the choice.A440 is now widely, though not exclusively, the standard for music around the world.

Pitch is also an important consideration in tuning systems, or temperament, used to determine the intervallic distance between tones, as within a scale. Tuning systems vary widely within and between world cultures. In Western culture, there have long been several competing tuning systems, all with different qualities. Internationally, the system known as equal temperament is most commonly used today because it is considered the most satisfactory compromise that allows instruments of fixed tuning (e.g. the piano) to sound acceptably in tune in all keys.