An interval is the distance between two notes. When the notes are played together they are called a Harmonic Interval, when played consecutively they form a Melodic Interval. By counting the number of alphabet letters from the bottom note up to the top note will give you the type of interval. eg from C to E is a 3rd (counting the letters C D & E) from C to A is a 6th (counting the letters C D E F G & A).

To determine the quality of the interval (eg Perfect, Major, Minor, Augmented or Diminished) one must consider the bottom note to be the major scale tonic and determine if the top note exists within that scale. eg from C to Eb is a 3rd ( C D & E) but as we are using C as the tonic of the major scale as our reference point, we must refer to the interval as a Minor 3rd as Eb is not a note in the C Major scale. To understand this it is important to know how to classify the quality of an interval.

Examples of Intervals