Intervals by Number & Quality
Naming intervals not just by number, but by their exact quality — major, minor or perfect — above and below a note.
Explainer
You already know how to count an interval's number. Now add its quality: 2nds, 3rds, 6ths and 7ths can be major or minor. Unisons, 4ths, 5ths and octaves are normally perfect.
A major interval made one semitone smaller becomes minor — C to E (major 3rd, 4 semitones) shrinks to C to E♭ (minor 3rd, 3 semitones).
You can also count both number and quality above AND below a given note. Above C, a 6th is A. Below C, a 6th is E.
The wider the interval, the further apart the notes sound — a 2nd is a close neighbour, an octave is the same note doubled in distance.
Worked examples
C to E: a major 3rd
4 semitones.
C to E♭: a minor 3rd
3 semitones — one semitone smaller than the major 3rd.
A 6th above and below C
Above: C D E F G A — A is a 6th above C. Below: C B A G F E — E is a 6th below C.