OocT 
120 %00 95 go 80 75 72 60 
120 120 120 120 120 120 129 I20 
which amounts to this: 
3 2 3 
I. z 
where all the poncords. are ao in . following order 
the third minor, the third major, the fourth, the fifth, che 
fixth minor, the fixth major, and laftly, the ona: 
By this table it is manifeft, that the oe concords are 
all contained between the octave and unifon. ey may 
even be heard all at once in the compafs of an otave with- 
tany mixture of difcords. Strike at the fame time thefe 
four founds, CE Ge 
the major fixth, which is compounded ; and will form 
other interval. Take any two of Fseine founds you pleafe, 
and the interval will be always confona It is from this 
union of all the concords, that the chord which they pro- 
duce is called the common or perfect ¢ 
The o€tave giving all the poco _confequently Sa 
all the fhades or differences, and b t means all t 
fimple intervals of our mufical fyitem ; ery aré but dove 
ations. The difference of the third major and the third 
minor gives the minor femitone ; 3 the difference of the third 
major and the fourth, the major femitone ; the difference 
of the fourth and fifth gives the tone major ; and the differ- 
ence of the fifth and fixth major gives the minor tone. 
the femitone minor and the femitone major, the tone minor 
and the tone major, are the only elements of all the inter- 
vals of m 
III. ee confonant found with one of the terms of the 
oGtave, is confonant alfo with the other ; oe every 
diffonant found with one is diffonant with the o 
IV. Finally, the o€ave has ftill this pee the moft 
fingular of all, that it may be doubled, tripled, and mul- 
tiplied at pleafure, without changing its nature, and with- 
out’ ceafing to be a perfe& concord. 
This multiplication of the o€tave, as well as its divifion, 
is however bounded with refpect to the powers of our 
organ of hearing; and an interval of eight octaves exceeds 
our appreciation. (See Compass.) e odtaves even 
oe pains 3 of their fweetnefs, by being multiplied; and 
n acertain meafure is paffed, all the intervals become 
Ife eafy for the ear to feize; a double oftave even becomes 
lefs agreeable than a fingle ; a triple than a double : in fhort, 
at the fifth odtave, the extreme diftance of the founds robs 
confonance of almoft all its charms. It is from the o€tave 
that we draw the order of all intervals by harmonic divi- 
fions and fubdivifivns. Divide the oftave harmonically 3 6 
by the number 4, and you will have on one fide the fourth 
3 4, and onthe other the fifth 4.6. Divide in the fame 
manner the fifth 10 15 harmonically, by the number 12, 
and you will have the minor third 10 12, and the — 
third 12 15. Laitly, divide the major third 72 90, a 
the tone,major 80 fhould be remem- 
bered, that thefe harmonical divifions give two unequal in 
Saale: of which the leaft is the grave and the greateft the 
acute. That if we make the fame divifions in arithmetic 
proportion, we have the fmalleft interval in the acute 
and t the grave. Thus the aa 2 4, di- 
aed withmetially, will firft give the 2 3 in the 
a 
calculate fou the length of the 
fringe. Thefe leoveries, indeed, are of little ule in them- 
I 
Now | 
0.cT 
as each ton femitones, 
the fame eae. divides itfelf alfo chromatically into twelve 
intervals of a femitone each, of whic even preceding 
eep their names, and the five others take the name of the 
ey diatonic found below by a fharp and above by a flat. 
e not fpeak here of diminifhed or fuperfluous oc- 
taves, beets ig seal admits of no alteration either 
in the melody arm 
It is pidaens in canpontion to admit of two fuccefflive 
octaves between two different parts, efpecially by fimilar 
motion; but that is admitted, and with an elegant effea, 
when done with defi gn and propriety through a whole air 
iod: thus, in many concertos all the ripieno parts 
play in o€taves or unifons. 
CTAVE, concerning the régle de odtave, fee REGLE 
or RULE. 
Octave, Diminifbed.. See DimintsHEep Odave, and In- 
TER vena 
» or OFabis, in rely denotes the eighth fay after 
any fealty ase: which {pace is alfo called u 
CTAVE, among the Romanifts, is ufed for the inate or 
period of eight days allowed for the celebration of a feaft, 
or fervice, in commemoration of fome faint, or on other 
folemn occafions. 
Eafter, Whitfuntide, St. John Baptift, St. Laurence, 
Epiphany, the Dedication, &c. are celebrated with oa 
The office in the o€tave is femi-double. 
OCTAVIA, in Biography, a Roman lady diftinguithed 
for her virtues and accomplifhments, was the daughter of 
Caius Octavius, the father of the emperor Auguftus. Sue- 
tonius indeed fays, ad the fame mother with that em. 
peror, but according to Plutarch, fhe was the daughter 
of a former wife of O€tavius. She was accordingly either 
fifter or half-fifter to the emperor. She was frit married 
to Claudius Marcellus, by whom fhe had two children be- 
fore his death, which happened a little after the war of 
Perfia, when fhe was pregnant of a third child. After 
this fhe married the triumvir Mark Antony, as the medium 
of reconciliation between him and her brother. At this 
time fhe was extremely beautiful, Eresend refpeGted and 
efteemed, and tenderly beloved by her brother. Anton 
while Antony 
went into the Ea as nit was, fays Plu nang ‘¢ that the 
work of all Aiieiles. love, and he love of Cleopatra, which 
have 
duty t 
her fituation as his wife: fhe colleG@ed confiderable fap 
for the war, in which he was engaged, and failed = 
t 
