I think Paul McCartney, of the Beatles, tells of working on a song with John Lennon, searching for the right chord to make a change. He would play various guitar or piano chords and suddenly Lennon would whirl around and say, "That's it!"

A key is comprised of the I, IV, and V, the 1, 4, and 5, the three principal chords of a key. The 6, or VI, is the relative minor.

Ringo brought "Octopus's Garden" to George Harrison with two chords, and Harrison advised that it takes 7 chords to play a song.

A vocal melody can work around one chord, or two, or three, or on up to seven, maybe more.

Who was the country songwriter who called a song, "Three Chords and the Truth" and wrote a book of the same name?

Some chords, in relation to others, are suited to the function of a verse, setting up the storyline, doing exposition of the story and/or characters, so other chords can up the intensity, the emotion, for the more summary, more specific lyric content of the chorus.

Some set mood for the melancholy, the whimsical, the dramatic, when played in relation to the others.

As you 'progress' from one to another their effects, relative to one another, may be apparent, and may be made more apparent by how the vocal melody, or instrumental accompaniment changes as the 'progression' changes.

Duke Ellington? Satchmo? Somebody said, "If it sounds good, it is good." If you can find chords that sound good, and develop them into a progression, sounding good together, you can create a musical work. If you can write a coherent, meaningful lyric to go with it, that makes a song.

There will always be another song to be written. Someone will write it. Why not you? www.garyeandrews.com