How to Play Thirds Up and Down Your Acoustic Guitar Fretboard

Many genres and guitar styles in American music are based on the all-important interval of a third. Melodies and solo lines are often constructed using thirds, and chord structures (for example, triads, and seventh chords) are built in thirds (sometimes known as tertian or tertial harmony). The type of third interval—major or minor—will determine the characteristic sound of the chord, whereas fifths and sevenths do not have the same degree of influence.

Weekly Workout is a series of monthly guitar exercises made up of interesting technical workouts that will get your fretting- and picking-hand fingers working in different ways, and offer musical studies that will help you visualize and explore the fingerboard.

In this Weekly Workout, you’ll learn different ways to map out and play thirds all over the fretboard. Lines based on thirds present great material for picking- and fretting-hand exercises, and also provide a solid foundation for melodic ideas and solos to explore in your improvising and writing (scroll down to view the music examples).

Week One: Playing and Hearing Both Types of Thirds

There are two types of thirds intervals: major and minor. A major third is the distance of two whole steps; a minor third is smaller, and equal to a whole step, plus a half step. Thirds can be played on the same string (Ex. 1a) or on adjacent strings (Ex. 1b). It’s important to hear, as well as see and feel, the differences between major and minor thirds. In these examples, C is the root; EH is the minor third, and E natural is the major third (two whole steps above C). However, these relationships are the same with any root, and they will look and feel the same on all adjacent strings, except for the G and B strings (Ex. 1c) due to the guitar’s standard tuning.

Ex. 2a shows a common scale pattern for a C major scale (C D E F G A B). You can think of the notes corresponding to numbers 1, 2, 3, 4, 5, 6, and 7. If you play every other note in succession, for example, C E G B D F A, then you are moving through the scale in thirds (Ex. 2b), and you can think of the numbers as 1, 3, 5, 7, 9, 11, and 13. Note that the scale degrees 2, 4, and 6 have become 9, 11, and 13 because they are now above the octave C (8)—this is why chord symbols only feature extensions of 9, 11, and/or 13. Ex. 3 illustrates an alternate pattern for a two-octave C major scale with the root on the low E string, as well as another option for moving across the strings in thirds. These examples are great guitar warm-ups, as they require some serious cross-picking to move up and down the strings.

Try Ex. 4, for instance, which features the notes of C major in a combination of the thirds and scale patterns in Ex. 3, ascending and descending, for a new workout challenge. Finally, Ex. 5 offers a killer workout by moving through C major in thirds, using four-note sequences. Incidentally, this particular exercise utilizes a pattern of diatonic seventh-chord arpeggios for C major, a favorite exercise among classical and jazz pianists.

Beginners’ Tip #1

Play these exercises very slowly, concentrating on clarity with every note. Start out by using strict alternate picking, especially as you move across the different strings. Try just one exercise per day before moving on to the next.

Week Two: Thirds in Seventh Chords

This week, you’ll work with the same concepts as you did in Week One, but now applied to minor and dominant-seventh chord types. Ex. 6 is the C Dorian mode (C D EHF G A BH) presented in thirds. Of course, you can play any scale or mode with thirds patterns; this example uses Dorian as it works well over minor seventh chords.

Ex. 7 combines the ascending thirds pattern starting on the low E string, but this time it descends in the Dorian mode in sequential pairs of thirds. These combinations are sometimes known as “broken thirds,” as they continuously move up and down through a scale. They are great exercises for both the fretting and picking hands. Ex. 8 shows an ascending-thirds fingering for a C7 chord—using C Mixolydian (C D E F G A BH) as the mode—starting on the fifth string. Ex. 9 uses the same ascending thirds/descending broken thirds pattern you see in Ex. 7, this time over a C7 chord.

In addition to using these lines for technical workouts, spend time improvising with these concepts over chord changes in your favorite songs. Ex. 10 uses the concepts from Ex. 6 and Ex. 7 over a basic Cm7–F7 chord vamp. Ex. 11 features a line that would work equally well in an up-tempo bluegrass song, or medium swing blues. The melodic line over G7 features an ascending line in thirds reaching up to the ninth of the chord before coming back down the scale. Then, a combination of broken thirds is used to rappel back down the C7 chord. These thirds concepts can help you break out of the dreaded “scale rut,” where solos tend to sound just like scales running up and down in stepwise motion.

Beginners’ Tip #2

In addition to the fingerings and patterns illustrated here, try coming up with your own fingerings, and write them down in a practice notebook. For example, instead of starting the pattern with your fourth finger (as in Ex. 7 and Ex. 9), you could start with your first or second finger and come up with your own patterns.

Week Three: Try Double Stops

Thirds also can be played concurrently, to create a vibrant sound known as double stops. Just as broken thirds alternate between major and minor thirds, double stops will either be major or minor, depending on the combination of notes. Ex. 12 harmonizes the first three notes of a C major scale, in thirds. This is a useful way to thicken up your sound, especially if you’re a solo performer or the only guitarist in your group. You can also add some chromatic motion in your double-stop line to create interest, as in Ex. 13. Jerry Reed and Chet Atkins were masters of employing double stops using thirds (and fourths) in their solos, and this technique works especially well in a country-roots setting.

Ex. 14 shows a double-stop line in thirds over a Cm7 chord, while Ex. 15 and Ex. 16 incorporate chromatic motion, dominant ninth sounds, and sliding over dominant seventh chords. There are a few different ways to pick double stops. Since thirds will always occur on adjacent strings, you could simply articulate both strings with a flatpick. Or, you could use hybrid picking with the pick on the lower note and the middle finger sounding the top note. Many country players opt for combining a thumbpick with the index finger, especially if they have a little bit of nail, which gets closer to the sound of a pick. Finally, fingerstyle players can find a comfortable combination of the thumb with the index/middle fingers. I recommend trying and practicing all of these approaches, so you’re ready for any musical situation.

Beginners’ Tip #3

Explore and map out double-stop ideas for all different types of chords so that you can effortlessly drop them in and out of a single-note solo.

Week Four: Chord Progression

The final workout shows some lead lines using all of the different techniques you’ve explored over the past three weeks. Ex. 17 features a common chord progression (I–ii–V–I) in the key of C. The first measure starts with some double stops built from a C major scale. The second bar outlines a Dm7 chord in thirds (essentially playing a Dm7 arpeggio up and down) before moving into a broken thirds line over the G chord, and then wrapping things up with more double stops (with a little chromatic move) over the resolving C chord.

Ex. 18 illustrates some of the same ideas over a minor-chord vamp. Notice the melodic arc that is created over Cm7 by ascending up in thirds before cascading back down in broken thirds to resolve to where the line started. Again, a great way to prevent your solos from sounding excessively scalar is to incorporate these concepts of thirds, broken thirds, and double stops. You’re still playing the notes in the scale, but presenting them in an interesting and creative way. 

Beginners’ Tip #4

Create several of your own melodic lines and patterns using the ideas in this lesson. Make sure to either write them down or record them so you don’t forget.