The name diabolus in musica ("the
Devil in music") has been applied to the interval from at least the early 18th century, 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'."Although the latter two of these authors cite the association with the devil as from the past, there are no known citations of this term from the Middle Ages, as is commonly asserted.