As quoted by Plutarch, in Lives as translated by J. Langhorne and W. Langhorne (1836), p. 84 http://books.google.com/books?id=UFROAAAAYAAJ&pg=PA84
Variant translation: 'Tis true, I never learned how to tune a harp, or play upon a lute, but I know how to raise a small and inconsiderate city to glory and greatness.
Plutarch's Themistocles, 2:3 http://data.perseus.org/citations/urn:cts:greekLit:tlg0007.tlg010.perseus-eng1:2 "...tuning the lyre and handling the harp were no accomplishments of his, but rather taking in hand a city that was small and inglorious and making it glorious and great" "...λύραν μὲν ἁρμόσασθαι καὶ μεταχειρίσασθαι ψαλτήριον οὐκ ἐπίσταται, πόλιν δὲ μικρὰν καὶ ἄδοξον παραλαβὼν ἔνδοξον καὶ μεγάλην ἀπεργάσασθαι." (at Perseus Project)