diapasons

Diapason is a musical term with two principal meanings. In organ terminology, it refers to the principal stop or rank of pipes that provides the organ’s core, bright, uncolored tone. Diapason stops are foundational to the instrument’s sound and are commonly available in several pitches, most often 8 feet (unison), with additional 4-foot and 2-foot ranks used to reinforce the ensemble. Variants include open diapason, which uses open pipes, and stopped diapason, which uses pipes closed at the end to produce a mellower timbre.

Beyond keyboard instruments, diapason also denotes the range or compass of a voice or instrument—the set of pitches it can realistically produce. In this sense, a singer’s diapason corresponds to their practical range, extending across the notes they can sing comfortably.

Etymology and usage: The term comes from French diapason, itself derived from Greek roots referring to “through all tones.” In English, diapason remains standard in organ building and music-specific writing, though outside specialized contexts it is more commonly encountered as a historical or technical term. The plural form diapasons may be used when referring to multiple diapason stops or ranges.