What is this secret chord number system? You’re hearing people talk about “One, Four, Five” chords progressions. And you’re seeing chords written as I, vi, ii, V, I. What the heck are they talking about?

Budding songwriter who wants to start writing your own songs? While some songwriters take a words-first, approach, many prefer to start with a chord progression to serve as the framework for the song and melody. So how do you know which chords to use in which order? Is there a formula for creating chord progressions?