adjective: extremely sharp or intense
adjective: very serious or severe
Ramsay
Of course, when these 25 sounds are heard as they arise in Nature, as a lovely halo of sound clothing one fundamental sound, it is not in the power of the human ear, as at present endowed, to distinguish them all; some ears will distinguish more, some fewer; but the likelihood is that the acute harmonics, as they are sometimes called in the scientific works on "Sound," are all there - at least sometimes - perhaps always; our limited powers of perception being the only defect. - Editor. [Scientific Basis and Build of Music, page 17]
Speaking of acute harmonics Pole says - "The first six are the only ones usually considered to be of any practical importance, and it is rarely possible to distinguish more than 10 or 12."
Mercenne (French, 1636) says - "Every string produces 5 or more sounds at the same instant, the strongest of which is called the natural sound of the string, and alone is accustomed to be taken notice of; for the others are so feeble that they are only perceptible to delicate ears . . . not only the octave and fifteenth, but also the twelfth and major seventeenth are always heard; and over and above these I have perceived the twenty-third and ninth partial tones in the dying away of the natural sound."[Scientific Basis and Build of Music, page 59]
musical vibrations in both acute and grave harmonics, generate a concentration of mighty action, an ever-outgoing of Nature's own power, so that she, by her own laws of vibratory motion, can reproduce and perpetually maintain outgoing power of action; and, again, play in perfect harmony her grand fugue with these tremendous all-resolving forces in that high and hidden and silent region in which Mr. Keely is experimenting. [Scientific Basis and Build of Music, page 87]
See Also