Introductions are not unfrequently found in the place of overtures before choral works, as in Handel's Joshua, Haydn's Creation, Beethoven's Mount of Olives, and Rossini's Stabat Mater. In this sense also the 'Vorspiel,' which Wagner so often adopts in place of an overture before his operas is an Introduction; as in Lohengrin and Rheingold, and the three operas of the Trilogy. In these the figures are generally very intimately connected with the music of the opera, and in all but the first they are part of the first scene, into whieh they pass without a break. In 'Tristan und Isolde' Wagner gives the name 'Einleitung' to the Orchestral prelude both of the first and second acts, and this term is yet more literally translateable as 'Introduction' than Vorspiel. In earlier operas the term Introduction is frequently applied to the whole first scene, as in Don Giovanni, Zauberflöte, Figaro, Freischütz, Il Barbiere, Norma, and so on. In Fidelio, Beethoven gives the name to the opening of the second act, which comprises more of an orchestral prelude, like Wagner's 'Einleitung.'
In relation to instrumental music again Introductions are occasionally found in other positions than at the beginning of an entire work; as for instance the preparatory adagio before the last movement of Beethoven's Septet and of his Symphony in C, the more important one in the same position in Brahms's C minor Symphony, the short passage before the slow movement of the 9th Sypmhony, the two notes which introduce the slow movement of the B♭ Sonata (op. 106), and the Introduction to the last movement of Brahms's Quintet in F minor.
INTROIT (Lat. Introitus, Antiphona ad Introitum, Ingressa). An Anthem, sung, by the Choir, at the beginning of High Mass, while the Celebrant, assisted by the Deacon, and Subdeacon, is engaged in saying the Judica me, Deus, and Confiteor at the foot of the Altar step.
The Introit is so called, not, as some have supposed, because the Cantors begin to intone it at the moment of the Celebrant's approach to the Altar, but, because it was antiently sung while the Faithful were entering the Church.[1] Its form has undergone many important changes. At present it consists of two distinct members: an Antiphon, and a Psalm. The words of the Antiphon, or Introit proper, are generally, but not always, selected from Holy Scripture. Of the Psalm, one verse only is sung, followed by the Gloria Patri, at the conclusion of which the Antiphon is repeated in full. Proper Introits are appointed for every day in the Ecclesiastical Year: and, from the first words of these, many Sundays derive the names by which they are familiarly known as 'Lætare Sunday,' the Fourth Sunday in Lent; 'Quasimodo Sunday,' the First Sunday after Easter, (Dominica in Albis—the 'Low Sunday' of the old English Kalendar). The music to which the Introit is sung is exclusively Plain Chaunt, and is given, complete, in the Roman Gradual. The antiphonal portion of every Introit has a special melody of its own. The Psalm is sung to a peculiar version of the Gregorian Tones, based upon, but considerably more elaborate than, that used for the Vesper Psalms. The Introit for the First Mass on Christmas day—which we would have transcribed, had space permitted—is a remarkably fine specimen of the style.
The manner of singing the Introit is as follows. The first clause is intoned when the Celebrant approaches the Altar, by one, two, or four Choristers, according to the solemnity of the Festival: which done, the strain is taken up by the full Choir, and continued as far as the end of the Antiphon. The first clause of the Psalm, and Gloria Patri, is then intoned, by the leading Choristers, and continued, in like manner, by the Choir; after which the Antiphon is repeated, as before. During Advent, Septuagesima, and Lent, it is sung, like the rest of the Mass, without any accompaniment whatever. At other Seasons, it is usually sung with the organ—but, always, so far as the voices are concerned, in unison.
No trace of the Introit is retained in the last revision of the Book of Common Prayer: though the first Prayer- Book of King Edward VI (1549) directs its use, in the form of an entire Psalm, followed by the Gloria Patri, but sung without an Antiphon. At first sight, the Rubric, 'Then shall he say a Psalm appointed for the Introit,' would lead to the supposition that the Psalm in question was not intended to be sung by the Choir: this idea, however, is disproved by the fact that the music for it is supplied in Merbecke's 'Booke of Common Praier Noted,' printed in 1550, and adapted, throughout, to King Edward's First Book.
N.B. Handel uses the word as a synonym for Intrada or Introduction. The autograph of 'Israel in Egypt' is headed 'Moses' Song. Exodus, Chap. 15. Introitus.'
INVENTION. A term used by J. S. Bach, and probably by him only, for small pianoforte pieces—15 in 2 parts and 15 in 3 parts—each developing a single idea, and in some measure answering to the Impromptu of a later day. [App. p.685 "Only the first set of pieces mentioned, viz. the 15 in 2 parts, are called by this name; the 3-part compositions are called 'Sinfonien.'"] [G.]
INVERSION. (Germ. Umkehrung.)
The word Inversion bears, in musical terminology, five different significations.
I. In Counterpoint it is used to signify the repetition of a phrase or passage with reversed intervals, or, as it is sometimes called, by contrary motion, e. g.—
Subject, or theme.
Inversion of subject, or theme.
This is a device very frequently adopted in the construction of fugues in order to secure variety. In J. S. Bach's fugues are many magnificent
- ↑ Martene. De Antiq. Eccl. Rit. 1. 131.
