One of the medieval church modes, also known as tetrardus plagis.
In ecclesiastical usage, dating from the incorrect application of Boethius's mode names to the system of church modes in the Alia Musica (c.870), the hypermixolydian mode is the diatonic octave-species from D to D with a final on G, in ascending order thus ("t" = whole-tone, "s" = semitone):
G A B C D E F G t t s t t s t
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