During the Hit Hacker's podcast, you often hear us talking about the chord progression for the song. Instead of using the chord names like G - C - D, we'll say "one, four, five." This is chord numbering, sometimes called Nashville Notation, and it's a simple way to describe chord changes without worrying about the song's key.

If you're not familiar with chord numbering, check out this simple explanation on playguitarmagazine.com or this more detailed explanation. Around the web and in magazines and books you'll see chord numbers presented in either Roman Numerals (I-IV-V) or arabic (1-4-5) -- they're the same concept.

The advantage of chord numbering for Hit Hacking is that you can compare songs and see how the chord progressions are similar or different, without worrying about the key they are in. For example, say the chords in a song are G-C-D in one song, and A-D-E in another song. They look totally different. But both use a 1-4-5 progression, just in a different key.

It doesn't require much beyond basic theory to learn and can really help you understand how songs work.