This outstanding book has over 300 chord progressions for you to write that hit! A chord progression or harmonic progression is a series of chords in a musical piece. From the common practise era of Classical music through the twenty-first century, chord progressions have been the cornerstone of harmony in Western musical heritage. Chord progressions are the cornerstone of Western popular music forms (for example, pop music and rock music), traditional music, and genres such as blues and jazz. Chord progressions are the distinguishing aspect of various genres, upon which melody and rhythm are created. Chord progressions in tonal music serve the purpose of establishing or opposing a tonality, which is the formal term for what is popularly referred to as a song's or piece's "key".