The Unison Interval (P1)
An interval is the distance between two notes, counted in semitones. Each of the thirteen simple intervals has its own page: reference songs that open with it, where it sits on the guitar fretboard, its inversion, and the chords built from it.
- The Unison (P1) — 0 semitones
- The Minor 2nd (m2) — 1 semitone
- The Major 2nd (M2) — 2 semitones
- The Minor 3rd (m3) — 3 semitones
- The Major 3rd (M3) — 4 semitones
- The Perfect 4th (P4) — 5 semitones
- The Tritone (TT) — 6 semitones
- The Perfect 5th (P5) — 7 semitones
- The Minor 6th (m6) — 8 semitones
- The Major 6th (M6) — 9 semitones
- The Minor 7th (m7) — 10 semitones
- The Major 7th (M7) — 11 semitones
- The Octave (P8) — 12 semitones
The unison spans 0 semitones — the same pitch — no distance at all. Measured up from a major-key tonic it lands on the 1st (the tonic itself), so it is diatonic to every major key. Inverted (the lower note moved up an octave) it becomes the octave.
The classic way to internalize it: sing a song that opens with it — Row, Row, Row Your Boat (the three repeated notes that open it); One Note Samba (a whole melody leaning on one repeated pitch). Then drill it on the ear trainer until you name it without thinking.