S E M 



S E M 



conftitutes the (harp edge of the inner ham-ftring, then goes 

 behind the internal condyle and the knee-joint, (ends off an 

 expanflon, which contributes to the formation of the aponeu- 

 rofis of the leg, turns round the head of the tibia, and fpreads 

 into a flat form to terminate on the anterior furface of that 

 bone, a little below the knee, behind the tendon of the far- 

 torius, and in company with that of the gracilis. Between 

 this tendon, and the internal lateral ligament of the knee- 

 joint, there is a burfa mucofa. The mufcle is covered by 

 the fafcia of the thigh, and at its origin by the gluteus 

 magnus : it covers the femimembranofus and the adduAor 

 longuj. The feraitendinofus afts on the knee, the hip, and 

 the pelvis, in the fame way as the femimembranofus does. 

 See the defcription of that mufcle. ■ 



SEMITERTIAN Fever. See Fever, Semitertian. 



SEMITONE, m Muftc, one of the degrees, or concin- 

 nous intervals, of concords. 



There are three degrees, or lefs intervals, by which a 

 found can move upwards and downwards fucceffively from 

 one extreme of any concord to the other, and yet produce 

 true melody ; and by means of which, feveral voices and 

 inilrumcnts are capable of the neceflary variety in paffing 

 from concord to concord. ' Thefe degrees are the greater 

 and lefs tone, and the femitone. The ratio of the firll is 

 8:9; that of the fecond 9:10. 



The ratio of the femitone is 15:16; its compafs is five 

 commas ; which interval is called a femitone, not that it is 

 geometrically the half of either of the tones, for it is more ; 

 but becaufe it comes foraewhat near it. It is alfo called the 

 iiaiural iem\tov\e, and the greater femitone, becaule greater 

 than the part it leaves behind, or its complement to a tone, 

 which is four commas. The Italians alfo call it feconda 

 tn'more, or a leffer fecond. 



There are feveral fpecies of femitones ; but thofe that 

 ii(ually occur in pradfice are of two kinds, diftingni(hed by 

 the addition of greater and lefs. The firft is expre(red by 

 the ratio of 16 to 15, or 14 ; and the fecond by 25 to 24, 

 or 44. The ocstave contains ten femitones major, and two 

 diefes, nearly ; for the meafure of the oftave being expreffed 

 by the logarithm i. 000000, the femitone major will be mea- 

 fured by 0.093109 ; and the oftave contains feventeen femi- 

 tones minor, nearly. If the meafure of the oftave be the 

 logarithm i.oooooo, the meafure of the femitone minor will 

 be o. 058894. Thefe two differ by a whole enharmonic diefis ; 

 which is an interval prafticable by the voice, and was much 

 in ufe among the ancients, and not unknown even among the 

 modern praftitioners. Euler, Tent. Nov. Theor. Muf. 

 p. 107. See Interval. 



Thefe femitones are caihdjiailious notes ; and with refpeft 

 to the natural tones, are exprelTed by charafters called ji?a/i 

 andjharps. 



Their ufe is to remedy the defefts of inftruments, which, 

 having their founds fixed, cannot always be made to anfwer 

 to tlie diatonic fcale. 



By means of thefe we have a new kind of fcale, called the 

 Semi TONIC Scale ; which fee. 



In praftical mulic, on keyed and fretted inftruments, it 

 is a nominal half-tone ; though mathematicians, in theory, 

 find it impoffible to divide a tone into halves. Roud'eau, 

 after explaining the fcientific and nominal dilference between 

 the major and minor femitone ; the major changing its place, 

 as e tof, and i to c ; and the minor remainm? on the fame 

 line, or on the fame fpace of the ftafF; "as Ft^ Fx<, Bb Bk^ ; 

 obferves, that though the imaginary change of tone is ex- 

 preded by the accident of a (harp or a flat, yet there is no 

 difference in the found of E« and Ft^, or in A* and Bb> on 



S 



the organ or harpfichovd, the fame tones being fometimes 

 major and fometimes minor, fometimes diatonic and fome- 

 times chromatic, according to the key we are in. 



For the importance of the femitone in mufic, fee Matthe- 

 fon's 6r89niflni»prob€, or Treatife on Thorough-bafe, where 

 he has bellowed many pages on this interval. Zarlino (;all« 

 it il/a/e, the fait, or feafonmg of mufic. 



The ufe of femitones has been much abufed of late, 

 by the now too common trick of running up and down the 

 piano forte in half-notes. Our flow chromatic is fundamen- 

 tal, and produftive of modulation ; but the quick chiefly 

 conillls of appoggiaturas, and mere notes of talle, unnoticed 

 in the bafe and the accompaniments. See Modern Chro- 

 matic. 



For the fober ufe of fucceflive femitones with good tafle 

 andeffeft, fee Mozart's Theme, N° 5. Var. 4. fecond flrain. 



SEMITONIC Scale, or the Scale of Semitones; a fcale 

 or fyltem of mufic, confifting of 12 degrees, or 13 notes, 

 in the oftave, being an improvement on the natural or diatonic 

 fcale, by inferting between each two notes of it another note, 

 which divides the interval or tone into two unequal parts, 

 Cdlled femitone. 



The ufe of this fcale is for inftruments that have fixed 

 founds, as the organ, harpfichord, &c. which are exceed- 

 ingly defedlive on the foot of the natural or diatonic fcale. 

 For the degrees of the fcale being unequal, from every note 

 to its ottave, there is a different order of degrees ; fo that 

 from any note we cannot find any interval in a feries of fixed 

 founds ; which yet is neceffary, that all the notes of a 

 piece of mufic, carried through feveral keys, may be found 

 in their jult tune, or that the fame fong may be begun in- 

 differently at any note, as may be neceflary for accommo- 

 dating fome infirumcnt to others, or to the human voice, 

 when they are to accompany each other in unifon. 



The diatonic fcale, beginning at the lowed note, being 

 firlt fettled on an inilrument, and the notes thereof diftin- 

 gui(hed by their names, a, b, c, d, c, f, g ; the inferted 

 notes, or femitones, are calhd JiSitious notes, and take the 

 name or letter below'with *, as c *, called c fharp ; fignify- 

 fying that it is a femitone higher than the found of c in the 

 natural feries ; or this mark b> called z flat, with the name 

 of the note above, fignifying it to be a femitone lower. 



Now .^ and ;-"4 being the two femitones the greater 

 tone is divided into ; and \^ and I4, the femitones the lefs 

 tone is divided into ; the whole oftave will ftand as in the 

 following fcheme, where the ratios of each term to the next 

 are written fraftion-wife between them below. 



fX. 



Scale of Semitones. 

 d. J». e. /. /«. g. g». 



flb- *• 



For the names of the intervals in this fcale, it may be 

 confidered, that as the notes added to the natural fcale are 

 not dcfigned to alter the fpecies of melody, but leave it 

 ftill diatonic, and only correft fome defefts arifing from 

 fomething foreign to the office of the fcale of mufic, viz. 

 the fixing and limitins^ the founds; we fee the reafon why 

 the names of the natural fcale are continued, only making 

 a diftinftion of each into a greater and lefs. Thus an in- 

 terval of one femitone is called a lefs fecond ; of two femi- j, 

 tones, a greater fecond ; of three femitones, a lefs third; of ll 

 four, a greater third, &c. " 



A fecond kind of femitonic fcale we have from another 

 divifion of the oftave into femitones : which is performed 

 by taking an harmonical meau between the extremes of the 



greater 



