The document discusses chord progressions that are commonly used in hit songs. It identifies the six main chords in the C major scale and explains that many popular songs use just 3 or 4 chords, most commonly the I, IV and V chords. Common 4 chord progressions are I-IV-V-vi and I-V-vi-IV. The document also provides tips on adding variation to chord progressions and choosing progressions that fit different music genres.