A Dictionary of Music and Musicians/Istesso Tempo, L'

by George Grove

ISTESSO TEMPO, L', 'the same time,' a caution in cases of change of rhythm or time-signature. It may mean that the measure remains as before while the value of the note changes—as in the change from 9-16 to 6-16 in Beethoven's Op. 111, or from 2-4 to 6-8 in 'Bagatelle,' Op. 119, No. 6; or that the measure changes while the note remains—as in Op. 126, No. 1; or that neither note nor measure change—as in Op. 111, 6-16 to 12-32, and Op. 120, Var. 3. Or that a former tempo is resumed, as in his Sonata, op. 110—'L'istesso tempo di Arioso,' 'L'istesso tempo della fuga.'

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