Remember that perfect intervals (unisons, fourths, fifths, and octaves) can never be major or minor, and major and minor intervals (seconds, thirds, sixths, and sevenths) can never be perfect in quality. However, any size of interval can be augmented or diminished.

All augmented and diminished intervals are considered dissonant. Perfect, major, and minor intervals have their own voice-leading procedures.

In modern Western Music, all of these intervals are considered to be pleasing to the ear. The intervals that are considered to be dissonant are the minor second, the major second, the minor seventh, the major seventh, and particularly the tritone, which is the interval in between the perfect fourth and perfect fifth.

If an interval is a half-step larger than a perfect or a major interval, it is called augmented. An interval that is a half-step smaller than a perfect or a minor interval is called diminished.

Unison, fourth, fifth and octave are called perfect intervals. Each of them can be diminished (one chromatic tone smaller) or augmented (one chromatic tone larger). The rest of the intervals within an octave are: second, third, sixth and seventh.

If it’s in the major scale and it’s a 4th, 5th or an 8ve then it will be a perfect interval. If it’s in the major scale and is a 2nd, 3rd, 6th or 7th then it will be a major interval. If it’s a semitone lower than a major interval then it will be a minor interval.

More Intervals

Main intervals

You can count any number of whole steps or half steps between notes; just remember to count all sharp or flat notes (the black keys on a keyboard) as well as all the natural notes (the white keys) that are in between. Example 4.2. The interval between C and the F above it is 5 half steps, or two and a half steps.

Two half steps

Two semitones (two half steps/half tones) make up one whole tone (one whole step). A whole tone can be from white to black, black to black, black to white or white to white key. For example, B to C#, F# to G#, Bb to C and C to D, respectively. There are two types of semitones.

Why do B and C and E and F not have a sharp note between them? Simply because, acoustically speaking, there is no room in our current system for another pitch between B and C, or E and F. A sharp always refers to raising the pitch by a half step, and a flat always refers to lowering the pitch by a half step.

Where is E or B Sharp? There is no definitive reason why our current music notation system is designed as it is today with no B or E sharp, but one likely reason is due to the way western music notation evolved with only 7 different notes in a scale even though there are 12 total semitones.

The reason why there is no black note on a piano between E and F – and B and C is a historical one to do with the evolution of the music and the piano. The notes in the major – or minor – scales are not equal divisions of the octave – they follow a mix of semitone then full tone jumps.

Fb is a white key on the piano. Another name for Fb is E, which has the same note pitch / sound, which means that the two note names are enharmonic to each other. It is called flat because it is 1 half-tone(s) / semitone(s) down from the white note after which is is named – note F.

G♯ major chords exist, so why don’t we ever see a G♯ major key signature? Simply put, it’s too complex for practical use, and there’s an easier way to express it: with the key of A♭ major (its enharmonic equivalent).