Major scale

Seven notes, in the order the whole system agrees on.

The default

The major scale is seven notes arranged in whole and half steps — the pattern every melody you've ever hummed is built on.

The formula

steps    W W H W W W H
notes    1 2 3 4 5 6 7
sound    bright, resolved, "home"

Why it matters

Chords come from scales. Stack the 1-3-5 of a major scale and you get the major triad. Every other scale is this one, altered.