When tones are played at the same time, their waves combine to form a [complex wave](https://imgur.com/a/y71Z1
). When the frequencies of those notes are in small ratios, like 2:1, 3:2, etc., the resulting wave is fairly simple and sounds pleasing. When the notes are in ratios involving larger numbers, like 16:15, the complex wave is more complicated and the sound is jarring and unpleasant.
An independent tritone is one that sounds pleasant and it suitable for ending a ~~people~~ piece. A dependant tritone is jarring and requires addition notes after it to "resolve" the music for the audience. They are often used to show alarm or distress. The diminished fifth, or the devil's triad, is an example of a dependant tritone.
Harmony is sourced from (closeness to) small close-integer ratios of frequency, where close-integers are only distanced by 1.
A perfect fifth is nearly 3/2, a perfect fourth is nearly 4/3, a major third is nearly 5/4, and they all have consonance. A major second is close to 9/8, which isn't all that small of integer. A minor second is not close to anything nicer than 16/15, but it is still useful in music.
A tritone is the square root of two, 1.414213...
That's not close to anything! It transcends dissonance, it is "ambiguous" because there is no closeness to any small close-integer ratio on which to evaluate it.
If you use a tritone, a diminished fifth, an augmented fourth, it will make the listener uncomfortable. You'd better be going for that.
In music, the “pitch” of a note refers to how “high” or “low” it sounds. Pitch corresponds to the frequency of a note (although the exact relationship has a couple of caveats).
We say that two pitches are “consonant” if the ratio of their frequencies is a simple fraction, and “dissonant” if the ratio is not a simple fraction. We care about this because our *brains* do — consonance might sound nice, stable, or pleasant, while dissonance may sound tense, unstable, or grating. In music, we use both of these effects.
In music, we call the ratio between the frequencies of two pitches the “interval” between the pitches. The simplest fraction (other than 1/1) is 1/2. We call the interval corresponding to this ratio the “octave”. Our brain likes octaves so much that two pitches separated by an octave sound very similar, though we can tell that one is higher and the other is lower.
In music, we say that pitches separated by octaves are in the same “pitch class”. In Western music, we use twelve different pitch classes. (The reason for this is interesting, but it's outside the scope of this answer.) In modern times, we consider all twelve of these pitch classes to be equally spaced.
With twelve pitch classes, we can form twelve different intervals. The smallest (other than the unison) is the “semitone”. An example of a semitone is the interval from C to C♯ (or, equivalently, to D♭. Another example is the interval from E to F. Other intervals can be represented as multiples of a semitone: from zero semitones (a unison) to twelve semitones (a full octave, which is equivalent to a unison when talking about pitch classes).
Some of these intervals are very consonant. The most consonant is the unison/octave, followed by the “perfect fourth” (five semitones) and “perfect fifth” (seven semitones). Other intervals are very dissonant, including the semitone itself (also called the “minor second”) and the “tritone” (six semitones, also called an “augmented fourth” or “diminished fifth” based on context). Because the tritone is so dissonant, it often sticks out to the listener. It should be used judiciously (which does not always mean sparingly!).
If you ever take a course in music theory, you'll hear about many “rules” to obey when writing music. These rules, prohibiting things like “parallel fifths”, are really practical guidelines; breaking them thoughtlessly will likely sound bad. The tritone itself has sometimes been fancifully called “the devil's interval”, although what was surely a hyperbolic description of its dissonance has taken a life of its own over the years. There is no evidence that this moniker was ever taken seriously in a religious sense, or that use of the interval was outlawed. It is, on the other hand, absolutely true that our standards of consonance and dissonance have mellowed over the years and that a listener from the year 1600 would likely have found the tritone interval much more grating than we do today — and that, therefore, a composer from that time would have used many fewer of them.
An important counterexample illustrates the point. One of the most important chords in common practice western music is the “dominant seventh chord”. This chord contains four notes, and two of them are separated by a tritone. The dissonance of this interval gives the chord a certain “tension”, and this tension is “resolved” when the dominant seventh chord is followed by a more consonant “tonic” chord. The most traditional, conservative way of ending a piece of music is with an “authentic cadence”, which often includes a dominant seventh chord. The lesson here is that even early composers did not avoid the tritone or dissonance in general; rather, they respected and often relied upon them.
Now, the disclaimer: I'm not an expert on early music (especially pre-Renaissance), so I'm open to input from someone with more specific expertise in that subject. Maybe there is some priest somewhere who once forbid the tritone in his church or something. Stranger things have happened.
Devil triton is just a flatted 5th on any major chord. So for example a Cmaj chord (C-E-G) with a flatted 5th is C-E-F#.
For a true Devils Tritone I believe you only play the 3rd+5th(E-F#) and no root(C) with sometimes a dominant 7th for more dissonance
That’s using Cmaj as an example
I was taught it is called the devil's tritone because you can go up the tritone and down the tritone and both intervals are of equal value. Thus, as the song says, there are two paths you can go by. That, and it just plain sounds sinister.