[LAN:ENUS]
[TITLE]INTERVALS
As we already said, each scale note is definited DEGREE and between degrees there are the INTERVALS, composed by a certain number of semitones.
Considering the C SDM (C,D,E,F,G,A,B), 3th degree is an E, 5th is a G, 8th is a C (as 1th, but more acute).

An interval number points to a specific degree and refers to a number of semitones. a FIFTH for a C SDM means that we're considering the G note (c,d,e,f, G ,a,b); this is important when we want to modify the pitch of a chord to produce a different sound for with same tonic. Changing some intervals value in a chord will make its sound more soft or hard, depending to the modifyed interval.
Once we have understood the most important intervals value, and how to change it, we'll be able to find every kind of scale or chord, just starting from a C SDM.

Intervals are divided in 5 categories: 
- perfect
- major 
- minor 
- augmented
- diminished 
 
and gets its their name from the following table, considering the C SDM and the harmonic relationship between notes:
1 C perfect
2 D major 
3 E major 
4 F perfect
5 G perfect
6 A major 
7 B major 
8 C perfect
 
Therefore we can say that among C and E there's a third major interval, and between C and B there is a major seventh interval. The harmonic relationship between notes remains the same for any tonality.

I.e. a THIRD MINOR considers the 3th scale degree lowered by 1 semitone. This means that we must subtract a semitone from the 3th scale note. In a C SDM, the 3th degree is an E: C, D, E; a C scale with a 3th minor will be C, D, Eb. For a D scale we'll have D, E, F instead D, E, F#.   

Keep in mind the main intervals, from the C SDM: TTSTTTS, and observe them for a good scale developement:
> major THIRD (2 tones)
> minor THIRD (1.5 tones)
> perfect FIFTH (3.5 tones)
> diminished FIFTH (3 tones)
> augmented FIFTH (4 tones)
> major SEVENTH (5.5 tones)
> minor SEVENTH (5 tones)

The third degree of a scale (3rd note) is definited characteristic, or modal, because it define the mode of the scale: major or minor.
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