SOUND. 



impulfe of the efficient caufe on the fonorous body, for a 

 longer or fliorter time, as in the notes of a violin, &c. which 

 arc made longer or Ihorter by llrokes of different length or 

 quickncfs. 



This continuity is properly a fucceflion of feveral founds, 

 or the effeft of feveral dilUndl ftrokes, or repeated impulfes, 

 on the fonorous body, fo quick that we judge it one con- 

 tinued found, efpecially if it be continued in the fame de- 

 gree of llrength ; and hence arifes the do6lrine of meaj'urc 

 and time. 



Sounds, again, are diftinguifhed, with regard to mufic, 

 vcAo JimpU and compound^ and that two ways. In the firft, 

 a found is faid to be compound, when a number of fuc- 

 ceflive vibrations of the fonorous body, and the air, come 

 fo faft upon the ear, that we judge them the fame continued 

 found ; as in the phenomenon of the circle of fire, caufed 

 by putting the fire-end of a ftick in a quick circular motion ; 

 where, fuppofing the end of the ftick in any point of the 

 circle, the idea we receive of it there continues till the im- 

 prefiion is renewed by a fudden return. 



A fimple found then, with regard to this compofition, 

 (hould be the effeft of a tingle vibration, or of io many 

 vibrations as are neceflary to raife in us the idea of found. 

 In the fecond fenfe of compofition, a fimple found is the 

 product of one voice, or one inftrument, &c. 



A compound found confifts of the founds of feveral dif- 

 tinft voices or inftruments, all united in the fame individual 

 time and meafure of duration, that if, all ftriking the ear 

 together, whatever their other differences may be. But in 

 this fenfe, again, there is a two-fold compofition ; a natural 

 and an artificial one. 



The natural compofition is that proceeding from the 

 manifold refleAions of the firft found from adjacent bodies, 

 where the refleflions are not fo fudden as to occafion echoes, 

 but are all in the fame tune with the firil note. 



The artificial compofition, which alone comes under the 

 mufician's province, is that mixture of feveral founds, which 

 being made by art, the ingredient founds are feparable 

 and dittinguifhable from one another. In this fenfe the 

 diftind founds of feveral voices or inftruments, or feveral 

 notes of the fame inllrument, are called fimple founds, in 

 contradiftindfion to the compound ones, is which, to an- 

 fwer the end of mufic, the fimples muft have fuch an agree- 

 ment in all relations, chiefly as to acutenefs and gravity, 

 as that the ear may receive the mixture with pleafure. 



Another diftinftion of founds with regard to mufic is 

 that, by which they are laid to he fmooth and even, or rough 

 and harjh, alio clear and hoarfe : the caufe of which differ- 

 encej depends on the difpofition and ftate of the fonorous 

 body, or the circumflances of the place ; but the ideas of 

 the differences mud be fought from obfervation. 



Smooth and rough founds depend principallyon the found- 

 ing body ; of thefe we have a notable inftance in ftrings 

 that are uneven, and not of the fame dimcnfion or conftitu- 

 tioii throughout. 



M. IVrrault, to account for roughnefs and fmoothnefs, 

 maintains, tlit-re is no fuch thing as a fimple found ; but 

 that the found of the fame chord or bell is a compound 

 of the founds of the feveral parts of it ; fo that where 

 the parts are homogeneous, and the dimenfions or figure 

 umfoim, there is always fuch a perfeft mixture and union 

 of all the founds, as makes one uniform and fmooth 

 found : contrary conditions produce harfhnefs. In cfTeft, 

 a likenefs of parts and figure make an uniformity of 

 vibrations, by which a great number of fimilar and co- 

 incident motion* confpir*: to fortify and improve each 



other, and unite, for the more effeftual producing of the 



fame effeft. 



This account he confirms from the phenomenon of a bell, 

 which differs in tone according to the part it is llruck in ; 

 and yet ffrike it any where, there is a motion over all the 

 parts. Hence he confiders the bells as compofcd of an in- 

 finite number of rings, which, accordinn^ to their different 

 dimenfions, have different tones, as choi ds or ftrings of dif- 

 ferent lengths have ; and when flruck, tno vibrations of the 

 parts immediately ftruck fpecify the tone, being fupported 

 by a fufficient number of confonant tones in other parti. 

 This muft be allowed, that every note of a ftringed inftru- 

 ment is the effeft of feveral fimple founds ; for there is not 

 only the found refulting from the motion of the firing, 

 but that from the motion of the parts of the inftrument, 

 which has a confiderable eff^eft in the total found, as is evi- 

 dent from hence, that the fame firing on different violin* 

 founds very differently. 



But Perrault affirms the fame of every firing itfelf, and 

 without confidering the inftrument. Every part of the 

 ilring, he fays, has its particular vibrations, different from 

 the grofs and fenfible vibrations of the whole ; and thetf 

 are the caufes of different motions and founds in the par- 

 ticles, which uniting compofe the whole found of the ftring, 

 and make an uniform compofition, in which the tone of the 

 particular part ftruck prevails, and all the others mix under 

 a due fubordination with it, fo as to make the compofitioi\ 

 fmooth and agreeable. If the parts be unevenly or irregu- 

 larly conftituted, the found is harfh ; which is the cafe in 

 what we cd^ falfe ftrings, and various other bodies, which, 

 for this reafon, have no certain and diftinft tone, but a com- 

 pofition of feveral tones, which do not unite and mil, fo 

 as to have one predominant to fpecify the total tone. 



As to clear and hoarfe founds, they depend on circum- 

 ftances that are accidental to the fonorous body ; thus, a 

 voice and inftrument will be hollow and hoarfe, if raifed 

 within an empty hogfhead, that yet is clear and bright 

 out of it : the effeft is owing to the mixture of other and 

 difterent founds, raifed by refleftions, which corrupt and 

 change the fpecies of the primitive founds. 



For founds to be fit to obtain the end of mufic, they 

 ought to be fmooth and clear, policfiing efpecially the firft 

 quality: fince, without this, they cannot have one certain 

 and difcernible tone, capable of being compared to others, 

 in a certain relation of acutenefs, of which the ear may 

 judge, and of confequence tbey can be no part of the ob- 

 jeft of mufic. 



Upon the whole then, with Mr. Malcolm, %ve call tliat 

 an harmonic or muftcal found, which, being clear and even, 

 is agreeable to the ear, and gives a certain and difcernible 

 tune (hence called tunable {mivi<\) , which is the iubjeft of 

 the whole theory of harmony. 



Dr. Burney, in the difcuffion of the fubjeft of this article, 

 obferves, that enquiries concerning the abfolute produftioi. 

 and modification of found belong to phyfics ; whereas a 

 mufician only examines founds comparatively one with the 

 other, and conlidcrs their proportions and relation as divided 

 into concords and difcords. (Sec Concord, Dikord, and 

 Rklation.) And it is only in this light, he fays, that we 

 fhall confider found in tlic rcliduc of this article. We Ihall 

 examine found under three different heads ; the tone, the 

 force, and the quality of tone. Under tliclc head;;, found 

 admits of modification : firft, from grave to acute ; fe- 

 condly, loud and foft ; thirdly, harfh and fwcet, or dull and 

 brilhant. 



We fhall firft eftablifh it as i principle, that whatever is 



the caufe of found, it* vehicle is the circumambient air ; 



3 D 7 hccaufe 



