This small glossary provides non-technical definitions for some terms which may be unfamiliar. If you would like another term to be added, please send your request using the contact form.

Comma

Singers, string players, trombone players, and players of other variable pitch instruments fine-tune pitches by ear in order to make music sound more in tune and more expressive. These tunings correspond to small intervals that are not indicated in music notation, and are generally excluded from modern music theory. The Greek word comma (meaning a small piece which is cut off) is used to describe these intervals, which average in size from around 20 to 30 cents. Commas have played a central role in the course of Western music history, but the comma has no presence on the modern keyboard; hence, there is no way to improve the tuning of a given chord or to expressively tune pitches during performance. To get a sense of the size of a comma relative to a piano, imagine a piano with each key divided into 4 parts (48 keys per octave). An average sized comma would be the interval between two keys on such a keyboard. [Also known by other names including Dieses, Limma, Syntonic Comma, Pythagorean Comma, Septimal Comma, and others]

JND

A Just Noticeable Difference or JND, is a small interval which ranges experimentally from 3 to 7 cents in size for both melody and harmony. The name JND comes from the fact that this interval is on the threshold of our perception; it is a change in pitch that is just, or barely, noticeable. In fact, under some conditions, the change in pitch will not be noticed at all, even on the wider side of the experimental range. To get a sense of the size of this interval relative to a standard keyboard, imagine a piano with each key divided into 17 parts (204 keys per octave). An average sized JND would be the interval between two keys on such a keyboard. Another way to think of the size of a JND is to divide an average comma into 5 parts. [Also known as a Difference Limen (DL) and sometimes a Frequency Difference Limen (FDL)]