In this lesson, I’m going to show you how to use thirds — double-note intervals — to add serious depth to your soloing. This is one of those guitar techniques that takes you beyond single-note lines and into something more melodic and musical. We’ll work through it in the key of F# minor (or A major, since they’re relative), using the second and third strings.

How Thirds Work on the Second and Third Strings

We’re using first inversion intervals — root on the bottom, harmony on top. On the second and third strings, a major third sits on the same fret for both strings. A minor third puts them one fret apart (the upper note is one fret higher). That’s the whole system.

Now, here’s how it maps to the major scale. Following the chord scale — major, minor, minor, major, major, minor, diminished, octave — we get intervals that follow the same pattern, except the seventh becomes just a minor interval instead of diminished. Starting from the A note on the third string, second fret: A major third is your starting point (same fret on both strings). Move up a tone and you hit B minor third. Then C# minor, D major, E major, F# minor, G# minor, and back to the octave A.

Breaking It Into Three Groups

You could run the whole thing up and down the fretboard from the 2nd fret to the 14th, and that’s a good place to start just getting the shapes under your fingers. But the real trick is breaking it into groups of three: major-minor-minor. That pattern repeats across the fretboard.

The first group starts at the 2nd fret. The same shape appears again at the 9th fret. And once more after that. Between these groups, there’s only one “leftover” interval at the 7th fret. So if you memorize that one three-note pattern — major, minor, minor — you’ve basically got the whole fretboard covered. That makes it easy to remember even if you don’t think in terms of note names or numbers.

Different Picking Approaches

You’ve got options for how to pick these. Playing both notes together (harmonically) with a single downstroke is the simplest approach. But you can also alternate — down and up — like the opening of “Brown Eyed Girl,” where you go through the intervals one-two-three-two-one. That’s a great starting point for this kind of playing.

You can also pick the notes individually using a down-up cadence. Try going through your three groups with different rhythmic subdivisions: one-e-and-a, two-e-and-a. Or simplify it to one-and-two-and. Changing the timing creates completely different feels from the same notes. If you want to work on the picking hand side of this, check out alternate picking for building that down-up consistency.

Mixing Thirds With Your Pentatonic Scale

Once you’ve got the three groups down, start mixing them with your F# pentatonic minor scale. The first three intervals sit right inside the pentatonic box at the 2nd fret. Move up to the 7th or 9th fret on the fifth string for the second group — that lines up with the next pentatonic position. The third group (the octave) drops right back into the F# pentatonic with the sixth string root.

This is where it gets musical. You’re not just running intervals up and down — you’re weaving them into your single-note lines, and suddenly your solos have this harmonic richness that wasn’t there before. You can reverse the direction, skip around between groups, or use one group as a repeating motif while your single notes fill in around it.

Practice With a Backing Track

The best way to internalize this is to play over a backing track. Start by just running the intervals up and down the fretboard to get the shapes memorized. Then work the three groups independently. Finally, start mixing them with your pentatonic scale and see what phrases come out. You can explore more adding flavor to your guitar solos once you’ve got these intervals under your fingers.

This is just the tip of the iceberg with double-note soloing. There are whole studies built around different interval approaches using backing tracks and themes — this is one approach that opens a lot of doors once you commit to it. Grab a backing track, work through the groups, and see where it takes you.