diap.

Noun

diapason (plural diapasons)

1. The musical octave.
   • 2 to 1, which is a duple ratio, forms the [symphony] diapason1818, Iamblichus, translated by Thomas Taylor, Life of Pythagoras, page 328
2. (broadly, literary) The range or scope of something, especially of notes in a scale, or of a particular musical instrument.
   • 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...

   Synonyms:

   range, scope

3. A tonal grouping of the flue pipes of a pipe organ.
4. One of the lowest strings on an archlute, theorbo, chitarrone, or similar bass lute-family instrument, usually unfrettable.
5. A harmonious outpouring of sound.
   • 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...1645, John Milton, “At a Solemn Musick”, in Poems of Mr John Milton, Both English and Latin