'solo' in the older services, we find 'full' and 'verse'; the former explains itself, but the latter is curious, and the origin of its use in this sense has never been satisfactorily explained. [See Verse.]
SESQUI. A Latin word, signifying, literally, the whole plus its half.
In musical terminology, the prefix Sesqui is used, in combination with certain numeral-adjectives, to express the Proportion, either of Harmonic Intervals or of rhythmic combinations. [See Proportion.] Thus, Sesquialtera expresses the Proportion of two to three, and therefore represents the Perfect Fifth, which is produced by sounding two-thirds of a given string. Sesquitertia, expressing the Proportion of three to four, represents the Perfect Fourth, sounded by three-fourths of the string. Sesquiquarta, or four-fifths, represents the Major Third. Sesquiquinta represents the Minor Third, given by five-sixths of the resonant string. Sesquisexta, six-sevenths, and Sesquiseptima, seven-eighths, correspond with no Intervals in the accepted Canon of the Scale: but, Sesquioctava, or eight-ninths, represents the peculiar form of the Major Second known to Theorists as the Greater Tone; and Sesquinona, nine-tenths, gives the Lesser Tone an Interval, which, though conventionally called a Major Second, and treated, in practice, as identical with that just described, is less, by one Comma, than the Tone represented by Sesquioctava.[1]
In rhythmic combinations, Sesquialtera is used as the general symbol of Triple Time. The term Sesquialtera is also applied to passages of three notes sung against two; Sesquitertia, to three notes sung against four; and Sesquiquarta, to four notes sung, or played, against five. [See Hemiolia.]
SESQUIALTERA. A compound organ stop consisting of several ranks of pipes, sometimes as many as five. Various combinations of intervals are used, but they only represent different positions of the 3rd, 5th, and 8th of the groundtone in the third or fourth octave above. The Sesquialtera thus gives brilliancy to the tone by reinforcing these upper partials.
The origin of the term Sesquialtera, as applied to an organ stop, is rather obscure. In the list of ratios given by Boethius, at the close of the 5th or beginning of the 6th century, which were exactly reproduced by almost every writer on music up to the 16th century, the term proportio sesquialtera signifies numbers having the ratio 2:3; the term therefore is really applicable to all stops having pipes at an interval of a fifth from the groundtone, such as the Quint, Twelfth, Larigot (nineteenth), etc. As stated above, the Sesquialtera organ stop does actually contain pipes having this relation, only, (it also contains pipes having the ratio 5:4 the tierce), which Boethius called a proportio sesquiquarta. On the whole it may be safely said that the word Sesquialtera was originally used for the purpose of showing that the stop contained pipes having ratios other than 2:1, or other than an octave-series.
SESTET or SEXTET (Fr. Sextuor; Ital. Sestetto). A composition for six instruments, or six voices, with or without accompaniment.
Instrumental sestets are of two kinds; those for strings only, which belong to the same class as string quartets and quintets, being monochromes in six real parts, and those for various combinations of strings, wind and pianoforte, which belong to the class of pianoforte quartets etc., and may be regarded as miniature symphonies. The first of these two classes is, naturally, but rarely met with, six-part harmony not being easy to write; but the few examples we have are striking ones. We may pass over Haydn's solitary specimen, called an 'Echo,' for 4 violins and 2 cellos, and mention only that of Spohr, in C (op. 140), a charming work; the two immortal compositions of Brahms (B♭, op. 18; G, op. 36), which stand at the head of modern chamber-music; the Sextet of Raff, op. 178, in G minor; and that of Dvorshak, recently introduced into England. Raff's work deserves more than a passing word, being one of that composer's most carefully written productions. It is a veritable triumph of counterpoint; not only is the labour of 6-part writing never for a moment shirked, but every device of imitation and canon is lavishly expended. One canon of 6 in 3 in the variations is particularly happy.
All the above are for 2 violins, 2 violas and 2 cellos. Turning now to the second and more comprehensive class, we find a few more in point of number but none of much artistic value. The prolific Boccherini wrote sixteen, Haydn one, Mozart only the 'Musical Joke.' Beethoven's Sestet for Strings and 2 obligate Horns (op. 81b) is interesting, but unfortunately impracticable for modern players.[2] His Sestet for Wind Instruments, op. 71 (for 2 clarinets, 2 horns, and 2 bassoons, in E♭), is an early work and little known. Beethoven himself mentions it in a letter of August 8, 1809, as 'one of my earlier things, and not only that, but written in a single night; perhaps the only thing in its favour is that it is the work of an author who has at least brought forward better works—though for many such works are the best.' (Nohl's Neue Briefe, No. 53.) Sterndale Bennett's Sestet for Piano and Strings a very early work (op. 8) is an elegant pianoforte piece with an unimportant though often picturesque accompaniment for strings, in which the piano has, perhaps, an undue share of work. Onslow left 2 sestets—ops. 30 and 77 bis.
It should be noticed that the sestets and quintets of Reicha and other composers, when written for wind instruments only, are practically quartets, one or more of the instruments taking a rest in turn.
- ↑ The Greater and Lesser Tones are, by some theorists, called the Acute and the Grave Major Second.
- ↑ A 1st Horn part is in existence, on which Beethoven has written '6tet of mine, God knows where the other parts are.' The slow movement has been adapted to voices as 'The Vesper Hymn,' and had a wide popularity in 'Orpheus.'
