# Augmented, diminished and the tritone

*Module 4 · Lesson 4: Intervals · BazzLow*

> Name intervals that are one semitone larger or smaller than usual, and recognise the tritone.

Before this lesson: [4.2 Major, minor and perfect](https://bazzlow.com/en/intervals/interval-qualities/)

Major, minor and perfect cover most intervals. Two more qualities cover the rest: one semitone larger, and one semitone smaller.

## Augmented and diminished

- An **augmented** (A) interval is one semitone larger than a major or perfect interval: C–F♯ is an A4; C–G♯ is an A5.
- A **diminished** (d) interval is one semitone smaller than a minor or perfect interval: C–G♭ is a d5; C–B𝄫 is a d7.

## The letters decide the number

Two intervals can have the same size and different names, because the letter names decide the number. These pairs are **enharmonic intervals**: they sound the same in isolation but behave differently in context. Chords and scales need the correct name (Modules 7 and 10).

*Pairs of intervals with the same size and different names, from C.*

| Interval | Name | Same size | Name | Semitones |
| --- | --- | --- | --- | --- |
| C–G♯ | A5 | C–A♭ | m6 | 8 |
| C–D♯ | A2 | C–E♭ | m3 | 3 |
| C–B𝄫 | d7 | C–A | M6 | 9 |
| C–F♯ | A4 | C–G♭ | d5 | 6 |

## The tritone

The **tritone** is 6 semitones: three whole tones. It is an A4 or a d5, depending on the spelling. It divides the octave exactly in half, and inverted it is still a tritone. In a major scale it occurs once, between the 4th and the 7th degree: F–B in C major.

The tritone sounds unstable, and it “wants” to resolve. That pull is the engine of the dominant seventh chord, which you will meet in Module 10.

> **Diagram:** Tritone shapes from C at fret 8 on the E string: F♯ on the same string, 6 frets up (fret 14), or on the next string up, 1 fret up (A string, fret 9). Both are the same pitch.

## Try it

Play F (fret 3 on the D string) and B (fret 4 on the G string) together: a tritone. Then move F down to E (fret 2 on the D string) and B up to C (fret 5 on the G string). The tension resolves.

## New terms

- augmented interval
- diminished interval
- tritone
- enharmonic interval

Page: https://bazzlow.com/en/intervals/augmented-diminished-tritone/