Open D7 is a variation on standard Open D tuning that gives you a dominant seventh chord when you strum all six strings open. This is a true blues sound — the dominant seventh is half major, half minor, which is why it works so well for blues slide guitar.
The Open D7 Tuning: D-A-C-F#-C-D
If you already know Open D major tuning (D-A-D-F#-A-D), getting to Open D7 is straightforward. You’re adding the flatted seventh (C) to create that dominant seventh sound.
Here’s the tuning from 6th string to 1st:
6th string: D (your root — keep this as the low bass note)
5th string: A (the fifth)
4th string: C (dominant 7th — drop the D down a whole step)
3rd string: F# (the major third)
2nd string: C (another dominant 7th — raise the A up a step and a half)
1st string: D (the root)
This gives you a “strong” dominant seventh because you have two strings tuned to the C — the flatted seventh appears twice, an octave apart on the 4th and 2nd strings.
Understanding Dominant 7th
The dominant seventh chord is unique because it contains both major and minor elements:
Major triad: D-F#-A (the three notes that make up D major)
Flatted seventh: C (a minor seventh interval from the root)
This combination creates that tension and bluesy quality. The dominant seventh can lean either way — it works for minor-related blues, but other artists use it in different contexts too. It’s a versatile, essential blues sound.
Why Two Seventh Notes?
You could tune to Open D7 with just one string on the flatted seventh. But having two C notes (4th and 2nd strings) gives you a stronger dominant seventh character. Wherever you put the slide, you get that seventh chord sound ringing through.
Getting There From Open D Major
If your guitar is already in Open D major (D-A-D-F#-A-D):
4th string: Lower the D down a whole step (two frets) to C
2nd string: Raise the A up a step and a half (three frets) to C
Everything else stays the same. The 6th, 5th, 3rd, and 1st strings don’t change.
Getting There From Standard Tuning
If you’re starting from standard tuning (E-A-D-G-B-E):
6th string: Drop E down a whole step to D
5th string: Leave as A
4th string: Drop D down a whole step to C
3rd string: Drop G down a half step to F#
2nd string: Raise B up a half step to C
1st string: Drop E down a whole step to D
Using Open D7 for Slide
The beauty of this tuning is that every position gives you a dominant seventh chord. Your slide creates that bluesy seventh sound automatically — no need to think about chord voicings.
Once you’re comfortable with the tuning, try a 12 bar blues in Open D7 to hear how it all comes together.
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