Bailly
ης (ἡ) v. ὕπατος.
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LSJ
(sc. χορδή), ἡ, the highest of the three strings which formed the framework of the musical scale (opp. νεάτη, μέση), but the lowest in pitch, Philol. 6, Pl. R. 443d, etc. ; αἱ ὑπάται the highest tetrachord, Anon. Oxy. 667.16; τὴν ἀπὸ τῶν ὑπάτων… ἐπίτασιν raising of pitch from the low notes, Antyll. ap. Orib. 6.10.7; τὸ βομβυκέστερον τῶν ὑπατῶν Nicom. Harm. 11; ὑπάτη ὑπατῶν ibid. (but ὑ. ὑπάτων Cleonid. Harm. 4).
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)