12 Bar Blues in Open G: Finding Your I-IV-V for Slide Guitar

If you’ve got your guitar tuned to Open G and you’re wondering “now what?” – the 12 bar blues is your answer. It’s the most common progression in blues, and Open G tuning makes it sound absolutely killer with a slide.

Let me show you exactly where your I, IV, and V chords live on the neck, and how to put them together into a progression that actually sounds like music.

Finding Your I-IV-V in Open G

First, you need to know the distance between chords. From the I chord to the IV chord is always 2½ tones (or 5 frets). From the IV to the V is one whole tone (2 frets).

In Open G tuning, that means:

I chord (G): Open position (or 12th fret)
IV chord (C): 5th fret
V chord (D): 7th fret

Let me break down how we get there: G to A is a tone, A to B is a tone, B to C is a semitone. That’s 2½ tones total – which puts your C chord (the IV) at the 5th fret. The D chord (V) sits two frets above that at the 7th.

Why the Octave Matters for Slide

Here’s something that trips up a lot of slide guitar players: you can’t slide down to an open string. The open position is already there – there’s nowhere to slide from.

That’s why knowing your octave (12th fret) is so important. You can use the open chord for your low rumbling rhythm, then jump up to the 12th fret when you want to slide into the I chord with some expression. It gives you options.

Watch: 12 Bar Blues Progression in Open G

The 12 Bar Structure

The standard 12 bar blues breaks down into three groups of four bars:

Bars 1-4: I chord (G – open or 12th fret)
Bars 5-6: IV chord (C – 5th fret)
Bars 7-8: I chord (G)
Bar 9: V chord (D – 7th fret)
Bar 10: IV chord (C – 5th fret)
Bars 11-12: I chord (G), with turnaround

Once you’ve got these positions memorized, you can play the 12 bar blues in Open G without thinking about it. Your hands just go where they need to go.

The Chromatic Turnaround

This is the most common closing riff in a 12 bar blues. You walk up chromatically from the IV to the V using a passing note:

C (5th fret) → C# (6th fret) → D (7th fret)

That’s your four, your chromatic passing note, and then your five. This walk-up creates tension that resolves beautifully when you land back on the I chord. You’ll hear this in countless blues songs – it’s essential vocabulary.

The 2-Bar Phrase Concept

One approach Colin emphasizes: think in 2-bar phrases. Two bars of rhythm strumming, then two bars of a slide riff. This gives the music a natural call-and-response feel.

So your first four bars of G might be:

Bars 1-2: Rhythm on open G
Bars 3-4: Slide fill around the 12th fret

When you move to the C chord, same structure – rhythm first, then fill. The key is to follow your chords with your slide riffs. Whatever chord the progression is on, that’s where your fill should be centered.

Mixing Open Strings with Slide Phrases

The real sweet spot in Open G slide is playing the open strings for your rhythm foundation while using the slide for melodic fills. Let those open strings ring out on the I chord, then slide into your IV and V positions for the changes.

This is where slide guitar really starts to sing – when you’re not just playing chords, but weaving between rhythm and lead seamlessly.

Same Pattern in Open D

Once you’ve learned these positions in Open G, you already know them in Open D. The fret relationships are identical – only the key changes. If you want to play songs in D, A, or related keys, check out the 12 bar blues in Open D. The muscle memory transfers directly.