22. The Tritone

Theory Lesson: Understanding Harmonic Tension

It is time to meet the most famous, unstable, and dissonant interval in music: The Tritone. It sits exactly in the center of an octave and is made up of exactly three whole steps.

The Visual Deception

The tricky thing about the tritone is that it does not have its own unique shape on the page. Depending on how the composer writes it, it will look exactly like a perfect 4th (called an Augmented 4th) or a perfect 5th (called a Diminished 5th).

You cannot spot a tritone just by looking at the blank note heads on the staff. You have to read the key signature or the accidentals (sharps and flats) next to the notes to know it is there.

The White Key Anchor (B to F)

There is only one natural tritone on the white keys of the piano: the distance between B and F (or F and B). Every other tritone on the keyboard requires you to press at least one black key. Because of this, B and F are your anchor points. If you are playing entirely on the white keys and see a 5th starting on B, or a 4th starting on F, you are playing a tritone.

How It Feels

Because a tritone almost always mixes a black key and a white key, your hand has to reach a little deeper into the keyboard. It sounds incredibly tense and dissonant. In traditional harmony, this tension always wants to resolve to a more stable, consonant interval like a 3rd or a 6th.

Self-Check Questions

1. Question: True or False: You can spot a tritone just by looking at the distance between the note heads on the staff lines.
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   Answer: False. Visually, it looks exactly like a 4th or a 5th. You must read the accidentals or the key signature to identify it.
2. Question: Which two white keys naturally form a tritone?
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   Answer: B and F (or F and B).
3. Question: What is the main musical function of a tritone?
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   Answer: It creates instability and harmonic tension that wants to resolve to a stable chord.