Have you ever noticed how certain chord progressions just... work? Like you hear them in song after song, and they always sound good?

There's a reason for that.

The I-V-vi-IV progression (1-5-6-4 in the Nashville Number System) shows up in literally hundreds of hit songs. We're talking The Beatles, U2, Journey, Bob Marley—the list goes on.

But here's what most guitarists miss: You can't recognize these patterns if you're only thinking in letter names.

When you see G-D-Em-C, you're looking at one specific key. When you see D-A-Bm-G, it looks completely different. But when you understand the number system, you realize they're the exact same progression—just in different keys.

That's the lightbulb moment.

Once you start thinking in numbers instead of just chord names, everything changes. You stop memorizing progressions in each individual key and start recognizing the pattern that works everywhere.

Someone plays a song in G? You hear "oh, that's a I-V-vi-IV." They move it to D for the singer? No problem—same progression, different chords.

This is what separates guitarists who can only play what's written from guitarists who can figure things out by ear and transpose on the fly.

I've watched students go from needing tabs for everything to being able to jump into jam sessions and just know what's coming next. Once the number system clicks, you start hearing music differently. You recognize the patterns instead of scrambling to find chord charts.

In the video above, I break down the most popular chord progression in modern music and show you exactly why the number system is the key to understanding songs across all keys.

And in Guitar Theory Unlocked, we go deep on this. You'll learn how to identify common progressions by ear, transpose instantly using numbers, and finally understand what musicians mean when they say things like "it's just a I-IV-V in A."

Because once you speak the language, the whole musical conversation opens up.

Checkout the other lessons in this series: