What is a Tritone? And, What Isn’t It?
- November 16, 2011
- By Michael Kaulkin
- Musicianship, Teaching
- 2 comments
The word tritone is frequently used interchangeably with the terms augmented fourth and diminished fifth. Let’s see if we can clear that up.
The intervals of the augmented fourth and diminished fifth indeed sound the same when played out of context on a piano, but they are not the same interval, they are not both the same thing as a tritone, and the tritone is not an inversion of itself.
The word tritone can be broken down to something like “three tones.” A major second, or whole step, is a tone. In music theory nerd circles, a major third, which is the combination of two whole tones, can be referred to at times as a ditone. So, the word tritone follows this pattern: three whole tones.
Now, is this an augmented fourth, a diminished fifth, or both?
I find it helpful to consider the visual layout of the piano keyboard. There’s no better representation of the arrangement of half steps and whole steps that is the diatonic scale. The two half steps that occur, mi-fa and ti-do, are plainly seen among the white keys. You will notice that the only occurrence of more than two sequential whole steps is between fa and ti, or F and B in C major.
The three whole tones make it kosher to call this a tritone. The four notes from F to B, inclusive, make it an interval of a fourth — an augmented fourth. In order to be a diminished fifth there would have to be five notes from the lower note to the upper one, inclusive. In C major, our white keys show us that this occurs between B and F.
So, we can correctly refer to the augmented fourth as a tritone, but not a diminished fifth. It’s easy to think the two are the same thing, because they sound the same when plonked on a piano with no context, but intervals have no meaning without context.
The presence of these half steps — mi-fa and ti-do — is what gives our diatonic system balance and drama, and these two intervals behave differently in light of that. The diminished fifth resolves inward — ti up to do and fa down to mi, while the tritone, or augmented fourth, resolves outward. In other words, these two intervals are as different from each other as, say, a major third and a minor sixth.
David Newman
Thanks for pointing this out, and now I’m curious how broadly the usage of this word has changed.
I cannot speak for higher level theorists, but in my ear training class, we use the word almost exclusively to identify the aug4/dim5 sound when it is out of context. My guess is that this is a common usage; otherwise one can merely state whether it was an augmented fourth or a diminished fifth.
I think, then, about words like “computer” which had a lot more relevant meaning half a century ago. Now, we use it to refer to a device many use primarily for word processing, surfing the internet, and listening to music. Or the word “gift” which once meant a dowry, but now has a more general meaning in English, and a more sinister meaning (“poison”) in German. Both apparently from the same origin.
I don’t know whether the meaning I ascribe to “tritone” is reflective of wider usage or not, but I think that for me, the meaning has clearly morphed into “the interval that can be written as either an augmented fourth or as a diminished fifth.” I would argue for the utility of such usage from the simple fact that we already have a term for an augmented fourth – “augmented fourth” – and that we have no better term to speak about the interval out of context.
I would also argue that such usage allows one to more easily talk about the interval in cases that encompass both expressions. (ie: “a jazz pianist can play through a circle of fifths by moving the tritone up or down chromatically.”) Without a notationally ambiguous word for that interval, it becomes harder to explain.
Of course, we can try to rebel against the morphed meaning of words, and my argument is practical, rather than academic. But I would encourage a move towards such usage, rather than away from it.
Michael Kaulkin
Thanks for your more practical take on this. Maybe the ideal approach is to explain the difference to students, but then not sweat it so much in day-to-day situations.
I do prefer to make a “thing” out of it, because I feel like not doing so is leaving something on the table that could potentially inform students’ insight about voice leading and function.