The Intervals

Taking the C major scale as a point of reference we can infer other intervals outside this key signature.

So starting from the C major scale the first two notes C and D make a major second interval, why? Because that's how they organized music theory and notation, every time you have two semitones between two notes that's a interval of a second, or you can think of it as a whole tone interval.

From that D to the next note E we also have a whole tone so another interval of a second, E to F only a semitone or half a tone so that's a minor second interval.

Then F to G another major second, the same for G to A and from A to B, and then a minor second from B to the next C on the next octave.

Now, thinking from C of the scale to all the other notes in the scale, we have from C to D a major second, from C to E a major third, that's two whole tones or four semitones. From C to F we have a perfect fourth, two whole tones and one semitone, or five semitones. Then we go from C to G and we have a perfect fifth, that's three whole tones and one semitone or seven semitones.

We get a major sixth from C to A, and counting we get four whole tones and one semitone or nine semitones. From C to B we get a major seventh, that's five whole tones and one semitone or eleven semitones. From C to the next C on the next octave we get an interval of an octave, that's six whole tones or more accurately five whole tones and two put apart semitones, one from E to F and the other from B to C.

Now outside this key signature, every time I add an accidental (flats and sharps) we will get different intervals from these ones.

Example: From C to Db we have a minor second, that's one semitone just like from E to F or like B to C.

We'll get a augmented fourth if we sharp the F, from C to F#, that's a augmented fourth also called the tritone also called a diminished fifth if we think of it as a C to a Gb note (That's a G flat). Originally in the C major scale we had a tritone from F to the note B. If we sharp the G note we get an augmented fifth, from C to G# (that's a G sharp).

We can also think of the C to G# as a C to Ab in which case we'll called it a minor sixth, from C to Bb we have a minor seventh just like in the original major scale the interval from D to C is a minor seventh or from E to D.

More complex and less intuitive are the augmented intervals, from C to D# is an augmented second, because of the name of the second note we have to call it a second instead or a third sense D# is the same auditory note as a Eb, so the augmented interval of a second sound and is the same thing as a minor third, but theoretically speaking they are different things.

Also the augmented third, for example is the same sonorous event as a perfect fourth, so from C to E# is the same as from C to F, sense E and F are only a semitone apart and if you sharp the E it has now became an F.

If we have an interval from C to A# that will be an augmented sixth also the same as a C to Bb the minor seventh.