diapason

plural diapasons

1. entertainmentThe musical octave.

   2 to 1, which is a duple ratio, forms the [symphony] diapason

   1818, Iamblichus, translated by Thomas Taylor, Life of Pythagoras, page 328

2. broadlyliteraryThe range or scope of something, especially of notes in a scale, or of a particular musical instrument.

   the piano curving like a conch, corollas giving out diapasons of light […]

   1934, Henry Miller, Tropic of Cancer, Grove Press, published 1961

   1 more example

   The glories and the beauties of form, color, and sound unite in the Grand Canyon—forms unrivaled even by the mountains, colors that vie with sunsets, and sounds that span the diapason from tempest to tinkling raindrop, from cataract to bubbling fountain.

   1895, J[ohn] W[esley] Powell, chapter XV, in Canyons of the Colorado, Meadville, PA: Flood & Vincent; republished as The Exploration of the Colorado River and Its Canyons, New York: Dover, 1961, →ISBN, →OCLC, page 397

   Synonyms: range, scope

3. entertainmentA tonal grouping of the flue pipes of a pipe organ.
4. entertainmentOne of the lowest strings on an archlute, theorbo, chitarrone, or similar bass lute-family instrument, usually unfrettable.
5. A harmonious outpouring of sound.

   he could hear nothing except the rattle of the crickets and the swelling diapason of the frogs […]

   1961, Graham Greene, A Burnt-Out Case

   1 more example

   That we on Earth with undiscording voice May rightly answer that melodious noise; As once we did, till disproportion'd sin Jarr'd against natures chime, and with harsh din Broke the fair musick that all creatures made To their great Lord, whose love their motion sway'd In perfect Diapason, whilst they stood In first obedience, and their state of good.

   1645, John Milton, “At a Solemn Musick”, in Poems of Mr John Milton, Both English and Latin