INTERVALS- Jazz explanation

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To understand any melodic or harmonic discussion, one must understand intervals. An interval measure s the space between two pitches. The smallest interval in Western music is the semitone or half step (either name may be used). This is the distance from one key to the next on the piano, for instance from C to C#.
The next-to- smallest interval is the tone or whole step. This is the distance between notes that are two keys apart on the piano. For instance, from C to D is a whole step. The semitone and tone form the basis for the measurement of larger intervals.

Interv al measurements have two parts: quantity and quality. The quantity, or numeric value, is determined by the musical alphabet: CD E F GAB. For example, the interval formed by the notes C and G will always be some type of 5th, regardless of the quality of Cor G (flat or sharp).
t C
a type of 6th D E F G
i- A
t B
a type of 4th C D
i- E
ta type of 2nd i- F G
Major and Perfect Intervals
The quality of an interval is determined by comparison with the intervals found in the major scale. When compared with a major scale, a whole step is found to be equal to the distance from the first to the second note, giving us yet another name for it: the major second.
It should be committed to memory that any major scale contains half steps (h) between scale degrees 3-4 and 7- 8, and whole steps (W) between all other pairs of notes. The half steps in any scale can be indicated with a wedge-shaped mark, or caret symbol ("). Here's the major scale in the key of C.
1 2 3 ~4 5 6 7~8 t (j 0 I) ~ 0 II 0 ~ 0 W W h W W W h
The distance from the root to the various pitches in the major scale form the basic intervals against which all others are measured. These eight intervals are divided into two basic types, perfect or major. \ • Perfect: unisons, 4ths, 5ths, octaves • Major: 2nds, 3rds, 6ths, 7ths t I' 0 Ij:eo # ~ ~ ~ Major Major Perfect Perfect Major 2nd 3rd 4th 5th 6th ~ Major 7th II ~ Perfect octave