Diapason

What it means

Diapason derives from the Greek dia pason (chordon), literally through all (the strings, or notes), and originally named the interval produced by moving through all the notes of a scale back to a repetition of the starting note: the octave. In ancient Greek music theory, diapason was one of the fundamental interval terms alongside diapente (fifth) and diatessaron (fourth).

Over the course of music history, especially in French, the term shifted from a pure interval name toward a second meaning: the reference pitch, the fixed pitch to which an ensemble or instrument is tuned (commonly called concert pitch in English). Because this reference pitch was in practice taken from and transmitted by a tuning fork, the French word diapason also came to denote the device itself, so that in French it can colloquially mean tuning fork as well.

Other names

Diapason should not simply be equated with the tuning fork as a tool: the tuning fork is the physical device that produces a pitch, whereas diapason originally denotes the octave interval and, in its extended sense, the fixed reference pitch as a musical quantity, independent of the tool used to produce it. It was only the close practical link between reference pitch and tuning fork in French usage that led to this overlap in meaning, which this entry deliberately makes explicit.