Tone is the resonance of a voice endowed with harmony. It is heightened in the acute, balanced in the grave, and broken in the circumflex. ― translation from: Thomas Davidson, The Grammar of Dionysios Thrax (1874), § iii: “On Tone”, page 4
the First is characterized from the first of the Circumflexed Conjugations, as from τιθῶ comes τίθημι; ― translation from: ibidem, § xviii: “On Verbs in μι”, page 13
ante AD 50, Philo (author), Leopold Cohn (editor), Περὶ τῆς κατὰ Μωσέα κοσμοποιίας in Philonis Alexandrini Libellus de Opificio Mundi (1889), § 41 (page 45, lines 11–14):
It also happens that all the changes of the voice amount to seven; the acute, the grave, the contracted, in the fourth place the aspirated sound, the fifth is the tone, the sixth the long, the seventh the short sound. ― translation from: Charles Duke Yonge, The works of Philo Judæus, the contemporary of Josephus I (1890), “A Treatise on the Account of the Creation of the World, as Given by Moses”, § xli, page 36