I was writing a song today and I discovered something very odd about chord progressions that I didn't know before, so I thought I'd share it.

I know, of course, that the chord prior influences the sound of the next chord. But what I didn't realize is that a chord several or even many measures prior can also influence the current chord.

Example: Writing in the key of G. The verse doesn't contain a C chord, but the chorus starts with a C. If I put a C chord ANYWHERE in the verse, even at the very beginning, which is a full eight measures prior to the beginning of the chorus, the (edit: CHANGE TO THE) C chord at the beginning of the chorus sounds notably different from when there are no C chords at all in the verse.

This astounds me. It feels a little like "spooky action at a distance," if there are any theoretical physics fans here -- Einstein's observation that electrons that are separated by even light years are influenced by one another.

This odd phenomenon also adds a whole new layer of complexity to choosing chords, whether for songwriting or for improvisation, jamming, etc. because it means that every chord in the song affects the sound of every other chord, and it's not just progressions that matter, but... collections? My head hurts...

Is this something that everyone knows but me? Is this something anyone else has experienced? Is there some sort of explanation for this?