You’ve learned how to play dominant 7th chords all over the neck. That’s great. But if you don’t understand how those chords work together in a blues progression, you’re still just moving shapes around. The I-IV-V progression is the foundation of every 12 bar blues you’ll ever play, and once you understand it, the fretboard starts making sense.
This is part 2 of our blues chords series, and today we’re talking about the I-IV-V—what it is, why it matters, and how your guitar is set up to make it easy to find these chords once you know the pattern.
📘 Blues Chord Mastery Series – Part 2 of 3
← Previous: Dominant 7th Chords Guitar | Next: Blues Chord Substitution →
What Is I-IV-V?
The I-IV-V progression is just three chords based on the first, fourth, and fifth notes of the major scale. In the key of A, that’s A (the I chord), D (the IV chord), and E (the V chord). Those three chords are the backbone of blues, rock, country—pretty much everything.
When you’re playing blues, those chords are usually dominant 7ths. So in the key of A, you’re playing A7, D7, and E7. If you’re in the key of E, it’s E7, A7, and B7. Different keys, same pattern.
The reason this works is because these three chords outline the major scale. They give you enough harmonic movement to sound complete without getting too complicated. That’s why the 12 bar blues has been around forever—it’s simple, it works, and it feels right.
How Your Guitar Makes This Easy
Here’s something most beginners don’t realize: your guitar is tuned to make finding I-IV-V almost automatic. The strings are tuned in fourths—except for the G to B string, which is a major third. That means when you stay on the same fret and move up one string, you’re moving up a fourth.
Let’s say you’re on the sixth string, fifth fret. That’s an A. Move up one string to the fifth fret on the fifth string, and you’ve got D—that’s a fourth higher. Now move up two more frets to the seventh fret, and you’ve got E. There’s your I-IV-V in the key of A, just from knowing one note and how the strings are tuned.
Once you understand that relationship, you can find your I-IV-V chords in any key, anywhere on the neck.
The I-IV-V in the Key of A
Let’s work through this in the key of A, since it’s one of the most common blues keys. If you’re playing in A, your I chord is A7. You can play it open, but for this lesson, we’re using the bar chord shape at the fifth fret—same shape we covered in part 1 of this series.
Your root note is on the sixth string, fifth fret. That’s A. So this is your I chord—A7.
Now you need your IV chord. That’s D. If you stay on the sixth string and move up five frets to the tenth fret, you’ve got D. Bar the same shape there, and you’re playing D7.
Or, here’s the shortcut: go up one string, same fret. Fifth fret on the fifth string is also D. From there, you can play D7 at the fifth fret if you want a different voicing. Either way works.
Finally, you need your V chord—E. From A on the sixth string, fifth fret, move up two frets to the seventh fret. That’s E. Play your E7 bar chord there, or drop down to the open E7 if you want that ringing sound.
So in the key of A, you’ve got A7 (fifth fret), D7 (tenth fret or fifth fret on the fifth string), and E7 (seventh fret or open). Those three chords are all you need to play a 12 bar blues in A.
The 12 Bar Blues Form
The 12 bar blues follows a specific pattern. It’s always 12 measures (or “bars”), and the chords change at predictable points. Here’s the basic structure in the key of A:
- Bars 1-4: A7 (the I chord)
- Bars 5-6: D7 (the IV chord)
- Bars 7-8: A7 (back to the I chord)
- Bar 9: E7 (the V chord)
- Bar 10: D7 (the IV chord)
- Bars 11-12: A7 (back to the I chord), then often E7 in bar 12 as a turnaround
That’s it. You play through that pattern, and you’ve played a 12 bar blues. Once you’ve got the chords down, the structure becomes second nature.
Why This Matters
Understanding I-IV-V isn’t just about memorizing a chord progression. It’s about understanding how chords relate to each other. Once you see that relationship, you can transpose to any key, you can follow other musicians without a chart, and you start hearing chord changes before they happen.
A lot of students learn songs without memorizing the structure underneath. They memorize where to put their fingers, but they don’t understand why those chords work together. When you understand I-IV-V, you’re not just learning one song—you’re learning the framework for thousands of songs.
Practice This
Don’t just read about it—play it. Pick a key and find your I-IV-V chords using the method I showed you. Start in A since it’s easy to find, but then try E, G, or D.
Once you’ve found the chords, play through the 12 bar blues form. Count out the bars, make the changes, and get comfortable with the pattern. You don’t need to play fast. You just need to play it clean and in time.
If you’ve got a backing track, use it. There are thousands of 12 bar blues tracks on YouTube. Play along and practice making those I-IV-V changes until they’re automatic.
What’s Next
📘 Blues Chord Mastery Series – Part 2 of 3
← Previous: Dominant 7th Chords Guitar | Next: Blues Chord Substitution →
This lesson is part 2 of a three-part series on blues chords. In part 1, we covered dominant 7th chords and how to move them around the fretboard. In part 3, we’ll talk about chord substitutions and variations you can use to make your blues progressions more interesting.
For now, get comfortable with I-IV-V. Find those chords in different keys, play through the 12 bar blues form, and make sure you understand how your guitar is laid out to make this easier. It’s one of the most important concepts you’ll ever learn on guitar.