Perfect intervals are different from major intervals in that they have only three possible qualities: Perfect, Augmented, and Diminished.
Notice that Perfect Intervals do not have a minor quality.
To review Intervals go to Understanding Intervals.
For review on Perfect Intervals go to Perfect Intervals.
In an earlier lesson we practiced these qualities using the unison and the 4th. Let's see what this looks like with the interval of a 5th.
Reminder: a key signature is just a short hand for all the accidentals in a key. The easiest way to know if a note is part of a scale is to have your key signatures memorized.
To review Major Key Signatures go to Major Key Signatures.
To review Major Scales go to Major Scales.
The bottom note is an A. Notice how the top note, E, is a note in the A major scale. In other words, there is no E♯ or E♭ in the key signature for the key of A. Therefore, this is a Perfect 5th (P5). (A perfect 5th is also the distance of 7 half-steps.)
Notice how the top note, E♯, is a half-step higher than the note in the A major scale, E (natural). In other words, there is a no E♯ in the key signature for the key of A and the E♯ is one half-step higher than the E natural in the key. Therefore, this is an Augmented 5th (A5). (An augmented 5th is the distance of 8 half-steps.)
Notice how the top note, E♭, is a half-step lower than the note in the A major scale, E (natural). In other words, there are no flats in the key signature for the key of A and E♭ is one half-step lower than the E natural in the key. Therefore, this is a diminished 5th (d5). (A diminished 5th is the distance of 6 half-steps.)