from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A full, rich outpouring of harmonious sound.
- n. The entire range of an instrument or voice.
- n. Either of the two principal stops on a pipe organ that form the tonal basis for the entire scale of the instrument.
- n. The interval and the consonance of an octave.
- n. A standard indication of pitch.
- n. A tuning fork.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. the range or scope of something, especially of notes in a scale, or of a particular musical instrument
from the GNU version of the Collaborative International Dictionary of English
- n. The octave, or interval which includes all the tones of the diatonic scale. Compare disdiapason.
- n. Concord, as of notes an octave apart; harmony.
- n. The entire compass of tones; the entire compass of tones of a voice or an instrument.
- n. A standard of pitch; a tuning fork.
- n. One of certain stops in the organ, so called because they extend through the scale of the instrument. They are of several kinds, as open diapason, stopped diapason, double diapason, and the like.
from The Century Dictionary and Cyclopedia
- n. In music: In the ancient Greek system, the octave.
- n. The entire compass of a voice or an instrument.
- n. Correct tune or pitch.
- n. A rule by which organ-pipes, flutes, etc., are constructed, so as to produce sounds of the proper pitch.
- n. A fixed standard of pitch, as the French diapason normal, according to which the A next above middle C has 435 vibrations per second. See pitch.
- n. A tuning-fork.
- n. In organ-building, the two principal foundation-stops, called respectively the open diapason and the stopped diapason. The open diapason has metal pipes of large scale, open at the top, giving that full, sonorous, majestic tone which is the typical organ-tone. The stopped diapason has wooden pipes of large scale, stopped at the top by wooden plugs, giving that powerful, flute-like tone which is the typical flute-tone of the organ. The most important mutation-stops of the open-diapason species are the double open diapason, sounding the octave below the key struck; the principal or octave, sounding the octave above; and the fifteenth, sounding the second octave above. Those of the stopped-diapason species are the bourdon, sounding the octave below; the flute, sounding the octave above; and the piccolo, sounding the second octave above. Many varieties of each of these occur. See stop.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. either of the two main stops on a pipe organ
The diapason, etc. _The diapason_ means here _the entire compass of tones_.
Now, the diapason is the ad interium, or interval betwixt and between the extremes of an octave, according to the diatonic scale.
D darkness of calamity dash of eccentricity dawning of recognition day of reckoning daylight of faith decay of authority declaration of indifference deeds of prowess defects of temper degree of hostility delicacy of thought delirium of wonder depth of despair dereliction of duty derogation of character despoiled of riches destitute of power desultoriness of detail [desultoriness = haphazard; random] device of secrecy devoid of merit devoutness of faith dexterity of phrase diapason of motives [diapason = full, rich, harmonious sound] dictates of conscience difference of opinion difficult of attainment dignity of thought dilapidations of time diminution of brutality disabilities of age display of prowess distinctness of vision distortion of symmetry diversity of aspect divinity of tradition domain of imagination drama of action dream of vengeance drop of comfort ductility of expression dull of comprehension duplicities of might dust of defeat
Fifteen Thousand Useful Phrases A Practical Handbook Of Pertinent Expressions, Striking Similes, Literary, Commercial, Conversational, And Oratorical Terms, For The Embellishment Of Speech And Literature, And The Improvement Of The Vocabulary Of Those Persons Who Read, Write, And Speak English
Les voix graves sont celles qui sont ordinaires aux hommes faits; les voix aiguës sont celles des femmes; les eunuques & les enfans ont aussi à-peu-près le diapason des voix féminines.
Drum, clarion, trumpet, and cymbal rung forth at once, and the deep and regular shout, which for ages has been the English acclamation, sounded amidst the shrill and irregular yells of the Arabs, like the diapason of the organ amid the howling of a storm.
The next discovery was that two strings of the same substance and tension, the one being double the length of the other, gave the diapason-interval, or an eighth; and the same was effected from two strings of similar length and size, the one having four times the tension of the other.
And where this love takes place there is peace and quietness, a true correspondence, perfect amity, a diapason of vows and wishes, the same opinions, as between 
Even when slavery was first introduced into this country, Fate had written upon the walls of the nation that it “must go,” and go it must, as the result of wise statesmanship or amid the smoke of battle and the awful “diapason of cannonade.”
Always this sort of man keeps up the pretence of highly distinguished and remarkable mental processes, whereas — have not I, in my own composition, the whole diapason of emotional fool?
P.S. #2: if 440 Hz is the frequency of a diapason La3 or La4, depending by your side of the Atlantic Ocean, so 3520 Hz is the last La of a piano keyboard.