well, one conclusive conclusion that can be drawn from this is that no useful conclusions can be drawn from Encyclopedia Brittanica articles. That bit about the tritone, though, is exceptionally bad.

The tritone is an essential harmonic interval, in use in its modern function since the Baroque, and in use in various cadence forms for at least a couple of hundred year prior to that. It's what makes a V7 chord resolve to I.

In folk music terms: when you play a G7 chord, followed by a C chord, you've used a tritone.

The idea of the "devil in music" in relation to the tritone is a corruption of a saying from medieval music theory, "Mi contra fa, diabolus est in musica". To understand what this means, you'll need to know a little about the medieval hexachord theory and practice.

Briefly, it doesn't imply anything at all about satanic properties of the interval, it means "be careful how you write parts, or the singers will fuck it up". It has all the diabolical significance of "i before e, except after c".

"Particularly offensive, or forbidden outright...until about 1900" -- sheesh, who publishes Brittanica these days, anyway -- Rupert Murdoch?