 The name "diabolus in musica" () has been applied to the interval from at least the early 18th century, or the late Middle Ages, though its use is not restricted to the tritone.Andreas Werckmeister cites this term in 1702 as being used by "the old authorities" for both the tritone and for the clash between chromatically related tones such as F and F, and five years later likewise calls "diabolus in musica" the opposition of "square" and "round" B (B and B, respectively) because these notes represent the juxtaposition of "mi contra fa".Johann Joseph Fux cites the phrase in his seminal 1725 work "Gradus ad Parnassum", Georg Philipp Telemann in 1733 describes, "mi against fa", which the ancients called "Satan in music"—and Johann Mattheson, in 1739, writes that the "older singers with solmization called this pleasant interval 'mi contra fa' or 'the devil in music'."