from the Fugue in Beethoven's Sonata in B♭, Opus 106.
The diminished seventh which is derived from the supertonic root is also common in various positions as (c) from the second of the Preludes in F minor in Bach's 'Wohltemperirte Clavier.'
As an example of an Imperfect Cadence which concludes on a chord other than the Dominant the following (d) from the slow movement of Beethoven's Violin Sonata in C minor, op. 30, will serve.
Occasionally the Imperfect Cadence appears to belong to another key, which is used transitionally on principles which are explained near the conclusion of the article Harmony (p. 682 a). The following instance is from Mozart's Quartet in G, No. 1.
in which case the two chords forming the Imperfect Cadence are the only ones not in the key of G in the whole passage up to the first perfect cadence, and cannot be considered as constituting a modulation.
The properties of the Imperfect Cadence were apprehended by the earliest composers of the modern harmonic period, and it is frequently found in works of quite the beginning of the 17th century. An example from Carissimi has been given above. In the instrumental music of the epoch of Haydn and Mozart and their immediate predecessors and successors it played a conspicuous part, as the system of Form in Music which was at that time being developed necessitated in its earliest stages very clear definition of the different sections and periods and phrases of which it was constructed, and this was obtained by the frequent use of simple and obvious forms of Perfect and Imperfect Cadences. The desire for continuity and intensity of detail which is characteristic of later music has inclined to lessen the frequency and prominence of cadences of all kinds in the course of a work, and to cause composers in many cases to make use of more subtle means of defining the lesser divisions of a movement than by the frequent use of recognisable Imperfect Cadences.
In Ellis's translation of Helmholtz the term 'Imperfect Cadence' is applied to that which is commonly called the Plagal Cadence. This use of the term is logical, but unfortunately liable to mislead through its conflicting with customary use. The common application of the term which has been accepted above is also not by any means incapable of a logical defence, but it must be confessed to be inferior both in accuracy of definition and comprehensibility to the expression 'Half-close,' which expresses admirably both the form of the succession of chords and the office it most frequently performs in music.
IV. For Imperfect Interval, see Iinterval.
[ C. H. H. P. ]
IMPRESARIO, L'. The title of the French adaptation (considerably altered) of Mozart's 'Schauspieldirector,' by Leon Battu and Ludovic Halévy, produced at the Bouffes Parisiens, May 20, 1856. This piece is said to have been mixed up with Cimarosa's 'Impresario in Angoscie' so as to form one piece by Goethe in 1791 while director of the theatre at Weimar.
[ G. ]
IMPROMPTU. Originally no doubt the name for an extempore piece; but as no piece can be extempore when written down, the term is used for pianoforte compositions which have (or have not) the character of extempore performances. The most remarkable are Chopin's, of which there are 4—op. 29, 36, 51, and 66 (Fantaisie-Impromptu in C♯ minor). The two sets of pieces by Schubert known as Impromptus—op. 90, nos. 1 to 4, and op. 142, nos. 1 to 4, mostly variations—were, the first certainly and the second probably, not so entitled by him. The autograph of the first exists. It has no date, and no title to either of the pieces, the word 'Impromptu' having been added by the publishers, the Haslingers, one of whom also took upon himself to change the key of the third piece from G♭ to G. The autograph of the second set is at present unknown. It was to these latter ones that Schumann devoted one of his most affectionate papers ('Gesamm. Schriften,' iii. 37). He doubts Schubert's having himself called them Impromptus, and would have us take the first, second, and fourth as the successive movements of a Sonata in F minor. The first does in fact bear the stamp of a regular 'first movement.' Schumann himself has Impromptus on a theme of his wife's, op. 5, and another Impromptu among his Albumblätter. Neither Beethoven, Weber, nor Mendelssohn ever use the word.
[ G. ]
END OF VOL. I.