The full set
Ordered by semitone count below. Each entry has a quick character note and the song mnemonic Aubel surfaces in-app. The three with full written guides are the first batch we've written up. We're adding the rest as we go.
- Unison Same pitch, played twice. Mnemonic: Unison reference (two pure notes)
- Minor 2nd One semitone. The leading tone resolving up (7 to 1, ti to do). Mnemonic: Jaws — main theme
- Major 2nd Two semitones. Adjacent scale degrees (1 to 2, do to re). Mnemonic: Happy Birthday to You
- Minor 3rd Three semitones. The defining interval of minor chords. Mnemonic: Smoke on the Water — main riff
- Major 3rd Four semitones. The defining interval of major chords. Read the guide →
- Perfect 4th Five semitones. 1 to 4 (do to fa), or 5 up to the next 1 (sol to do). Mnemonic: Here Comes the Bride (Wagner)
- Tritone Six semitones. The 4-to-7 (fa to ti) inside dominant 7 chords. Wants to resolve outward. Read the guide →
- Perfect 5th Seven semitones. 1 to 5 (do to sol). The strongest tonal move. Read the guide →
- Minor 6th Eight semitones. 5 to the flat 3 above. Inversion of the major 3rd. Mnemonic: The Entertainer (Joplin)
- Major 6th Nine semitones. 1 to 6 (do to la). Inversion of the minor 3rd. Mnemonic: My Bonnie Lies Over the Ocean
- Minor 7th Ten semitones. The flat 7 of the dominant 7 chord. Mnemonic: Somewhere (West Side Story)
- Major 7th Eleven semitones. 1 to 7 (do to ti). One semitone shy of the octave, leaning up. Mnemonic: Take On Me — chorus
- Octave Twelve semitones. Same pitch class, frequency ratio 2:1. Mnemonic: Somewhere Over the Rainbow
How they unlock
Aubel starts new players on four intervals: unison, perfect 4th, perfect 5th, and octave. Those four are far enough apart that they rarely get confused with each other in the first week. The major 3rd unlocks once rolling accuracy on the starter pool sits above 70%. Then major 6th, then the rest of the major and minor pairs, then the harder ones at the edges (minor 6th, minor 7th, major 7th, and the tritone).
The order isn't arbitrary. It's the sequence that minimises early confusion. Each new interval has at least one anchor already in your ear before it shows up.
A few things that confuse most people
Enharmonic equivalents: an augmented 4th and a diminished 5th sound identical. Both are tritones. The two names matter for notation, not for ear training.
Inversions: every interval pairs with one other interval that sums with it to an octave. The major 3rd pairs with the minor 6th. The perfect 4th pairs with the perfect 5th. Inverted intervals sound related, not identical.
Compound intervals: distances larger than an octave (a 9th, 10th, 11th, 13th) collapse back to their simple form for ear-training purposes. A major 10th is an octave plus a major 3rd. The 13 intervals on this page cover everything.