Unison & Octave Intervals

The first thing to know about these two types of intervals is there are three kinds of each. These three kinds are: perfect, diminished, and augmented. When I took music theory nobody explained this to me and I was totally lost but there is no reason to fear these types of intervals. My teacher at the time was also partially deaf in one ear....and she tried telling me that I couldn't hear pitch right...lol. 

Anyway, perfect, diminished, and augmented will later be applied to 4th and 5th intervals.

For perfect unisons there are 0 half steps between the notes. In other words it is the exact same note.

For example, C = C

This is called a perfect unison.

Diminishing consists of lowering the note by half a step.

For example, A = Ab

This is called a diminished unison. 

Augmenting is the opposite and raises the note by half a step.

For example, D = D#

This is called an augmented unison.

A tip to remember the difference between augmented and diminished is to remember that 'diminish' means to lessen or to reduce. Then, you'll know that augmented is the opposite.

These modifiers to the notes are only applied to unisons, fourths, fifths, and octaves. 

Now on to octaves. 

A perfect octave is 12 half steps. 

G to G

F to F

A diminished octave is 11 half steps.

G to Gb

B to Bb

An augmented octave is 13 half steps. 

A to A#

C to C#