[1] Similarly glossed in other lexica; evidently quoted from somewhere (perhaps Philo Judaeus, where it occurs several times).
[2] M.L. West, Ancient Greek Music (Oxford 1992) 160: "All scales (according to Greek theory) are built up from 'tetrachords', that is, from systems of four notes spanning a fourth. Successive tetrachords were either 'conjunct', that is, with a shared note (for example, d-g-c), or 'disjunct', separated by a tone (for example, d-g: a-d)".