In a ruler I have 1cm, 2cm, 3cm, 4cm, etc.
Why isn't there in music: 1st, 2st, 3st, 4st, etc. (where st = semitone)

But instead we have:

Minor second, Major second, Minor third, Major third, Perfect fourth, Perfect fifth, Minor sixth, Major sixth, etc..

Why are they called with such long complicated names? (major,minor,perfect), and why do they add an additional semitone in the name? (example: we say "minor second" but it's just 1-semitone.. so shouldn't it be called a "minor first". or just call it a first. or just a 1st :))

  • The major / minor / perfect is a useful indication though I feel that the second is misnamed as the second in a minor scale is major. If I were to object, it would that the numbers are wrong: they should all be one less. A third plus a third is a fifth and not a sixth as you might expect.
    – badjohn
    Commented Apr 26, 2017 at 16:28
  • What's the additional semitone in the name? Complicated with only two words?
    – Tim
    Commented Apr 26, 2017 at 16:33
  • 1
    If you want to count distance, then you can of course use semitones -- and you will be understood. Intervals are describing relationships.
    – user28
    Commented Apr 26, 2017 at 17:52
  • @badjohn: I see what you mean about the quality of the interval, but the central terms are major (for 2nd, 3rd, 6th, and 7th) and perfect (for 4th, 5th, and octave). Minor is always one half-step shy of major, diminished is one half-step shy of minor or perfect, and augmented is one half-step over major or perfect.
    – Brian Tung
    Commented Apr 26, 2017 at 23:14
  • @badjohn: As for the numbers, I'm sure that's historical. The fact that they're given ordinal names is a clue: In C Major, D is the second note, E is the third note, etc., so C-D is a second, C-E is a third, etc.
    – Brian Tung
    Commented Apr 26, 2017 at 23:15

2 Answers 2


Because an interval is not a raw distance, it's a measurement of different properties of a note one which is a raw distance in semitone and the other is the raw distance in letter name. While the raw distance is mathematically useful, it lacks the contexts which musicians understand constructs like chords, scales, ect.

Let's look at the famous example which would be the difference between an augmented 2nd and a minor 3rd. A very common interval you'll see in any minor scale is a minor 3rd which would be a C to E♭. The raw distance of this is 3 semitones above the original, however there is another interval that can occupies this space which is a #9 which is also 3 semitones up (after a modulo 12) which would be a C to D♯. So if you are playing a C7♯9 you would describe the interval of the 9th differently then you would if it was a 3rd.


It's because of the system of harmony that is based around major and minor scales, triads and their extensions - the whole functional harmony thing. However hard the modernists try to insist that this system is dead, people WILL keep writing melodies based on the major scale, and describe other modes in relation to it. And they WILL keep basing their harmonies on triads.

  • If it ain't broke...
    – Tim
    Commented Apr 26, 2017 at 21:37

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