An Interval is the distance between two notes. Intervals occur in two general types: Harmonic, when the notes
are sounded simultaneously, and Melodic, when the notes are sounded separately. Whether harmonic or melodic,
intervals are measured and classified by their Numerical Distance and Quality.

Numerical Distance
        The numerical distance of an interval is determined by the number of letter names between them.
C-D is a second, C-G is a Fifth, etc.

Interval Quality
        The five most common interval qualities are: Perfect (P), Major (M), Minor (m), Augmented (+), and
Diminished (o). Less frequent qualities are Doubly Augmented (++), and Doubly Diminished (oo).
        Only the Unison, 4th, 5th, and Octave can be Perfect intervals - but never mjor or minor. The 2nd,
3rd, 6th, and 7th can be major or minor, but never perfect. The quality of all numerical distances,
however, may be Augmented or Diminished.
 

-If you raise a perfect interval one ½ step, it becomes Augmented.
-If you lower a perfect interval one ½ step, it becomes Diminished.
-If you raise a Major interval one ½ step, it becomes Augmented.
-If you lower a Major interval one ½ step, it becomes Minor.
-If you lower a Minor interval one ½ step, it becomes diminished.
-Always analyze intervals from the lowest note.
-Always analyze intervals in the key of the lowest note.
 

Sounds- This is the way I associate intervals. Other people may have different ways. Use what works for you.

 P1- Perfect Unison- Exact Same Note
 m2- Minor Second- Jaws, ½ Step, Chromatic Scale
 M2- Major Second- Whole step, Major Scale, Chopsticks, Happy Birthday
 m3- Minor Third- Brahms Lullaby, New World Symphony
 M3- Major Third- 1st two notes of a major triad, Rocky, Barbara Ann, Jolly Old St. Micholas
 P4- Perfect Fourth- Wedding
d5 or A4- Diminished Fifth or Augmented Fourth (A4 is more common)- West Side Story-Cool,
        West Side Story- Maria
P5- Perfect Fifth- Star Wars, Superman, Aladdin, JFK, The Rose
m6- Minor Sixth- Hulk Theme, Beethoven’s Moonlight Sonata, Frankenstein
M6- Major Sixth- Bonnie, It Came upon a Midnight Clear, NBC, Beginning of Angel of Music
m7- Minor Seventh- Star Trek opening, West Side Story
M7- Major Seventh- Somewhere over the rainbow (3rd Note), Near Octave (dissonance)
P8- Perfect Octave- Octave