Shouldn't all music intervals have five names?

Question

Shouldn't technically all intervals have five names? (Maybe with few exceptions where it goes below zero semitones but still I can't see why it can't go below zero semitone when it can be played) With these five possible cases: 1. ♯Note-♭Note ( n semitones ) 2. ♯Note-Note or Note-♭Note (n+1 semitones ) 3. Note-Note ( n+2 semitones ) 4. Note-Note♯ or ♭Note-Note ( n+3 semitones ) 5. ♭Note-♯Note ( n+4 semitones )

Answer 1

Hi there, you are correct that intervals have many names. While this holds true when analyzing notes and intervals one must adhere to the written notes on the page. Although the notes C》E and C》F-flat will ultimately sound the same notes when written one must call these intervals different names. C》E is a Major 3rd but C》F-flat is a Diminished 4th. However, if one we just to listen to the interval both answers would be correct (but major 3rd being the more acceptable answer) as there is no way to distinguish the difference when heard.

Hope this helped!

Answer 2

In post-tonal music, technically, they do. Or can. It's only in post-tonal music, though, where the definition of an interval (or rather interval class) is only the number of semitones it spans. Even there, it would have to be a cruel or incompetent composer who would ask a performer to play an interval spelled E-double-flat to F-double-sharp instead of D to G.

In the more familiar tonal contexts, the size of an interval really describes how many letter names (scale degrees) it spans. Both B-flat to D-flat and B-flat to C-sharp span three semitones; but the first, a minor third, is a consonant interval in the context of scales that have both those notes (such as 3 and 5 in G-flat major), whereas the second is probably 6 to 7 in D harmonic minor, a dissonant interval.