A Dictionary of Music and Musicians/Impromptu
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.
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