Most simple melodies can be harmonized using just the I, V7 and IV chords. Many times, you only need I and V7.

• The I chord uses scale degrees 1, 3, and 5.
• The V7 chord uses scale degrees 5, 7, 2 and 4.
• Notice that scale degrees 1, 2, 3, 4, 5 and 7 are in the I and V7 chords. This is every note of the major scale except for scale degree 6.
• The IV chord uses scale degrees 4, 6 and 1, so if you use I, V7 and IV you can harmonize any tune that is built on a major scale. You can use IV most effectively when the tune has a strong scale degree 6 or strong scale degree 4.

CHORD	Scale degrees	Name	Characteristics
I	1, 3, 5	Tonic	Finality Resting Consonance
V or V7	5, 7, 2 or 5, 7, 2, 4	Dominant or Dominant-seventh	Pulls toward finality Movement V7 has more dissonance
IV	4, 6, 1	Subdominant	Not final Less resting than I Consonance