In music, an interval is defined as the distance between two notes. The intervals of thirds and sixths are of particular interest, as they’re the building blocks of the chords we use in Western music. Playing notes together in thirds and sixths—often referred to as double-stops—is a lot like singing a harmony against the melody of a song. It just takes two strings and two fingers to make this kind of fun on ukulele. In this short and simple lesson, you’ll explore thirds and sixths in the ukulele-friendly keys of F and C major.

Start in the Key of F

Before tucking into Example 1, strum an open F chord (first finger on string 1, fret 1 and second finger on string 4, fret 2). Then, play each pair of two notes together on strings 1 and 2—all notes derived from the F major scale (F G A Bb C D E). Try this a few times to get used to traveling up and down the neck. Playing the chord first helps to ground your ear such that you can hear the harmonies move within the key, so do that for each example in this lesson. 

The first notes in Ex. 1 are F and A. In the F major scale, there is a G in between the notes F and A, so we call this harmony a third because we skipped the second note. The second set of notes are G and Bb, so we bounced over the A this time to create the next pair of thirds. As you can see, this exercise creates a pattern on the fretboard: the major thirds are one fret apart; the minor thirds, two frets. By playing major and minor thirds in a specific order, you can outline any key, but we’ll stay in F for now and explore what happens each time we play two different sets of strings. 


Now play through Example 2 and notice what has changed from Ex. 1. This time, the notes are exactly the same, but the pattern is different and the strings aren’t adjacent. In reentrant tuning, the higher note is on the fourthstring, but if you’re using a low G, the harmony will still work—it will ring an octave lower, at the same fret, creating a sixth. This time, the pattern is at the same fret for major thirds and one fret apart for minor. 

The good news is that there are only two ways thirds and sixths patterns work on ukulele for any given string set: patterns where they are apart by one or two frets and those where they share the same fret or are one apart. Be aware that when sixths on strings 1 and 4 are played together, the spaces apart go the opposite direction! Now it’s time to explore Examples 3–6. Each figure visits a specific set of strings to produce thirds or sixths within F major. 

Move On to C

When you get a good feel for the key of F, move on to Examples 7–12, which are in the key of C major,and look for familiar patterns. As you did with the examples in F, play an open C chord (third finger on string 1, fret 3) before exploring the intervals. The same patterns all start in different places, but you’ll pick them up quickly once you’ve spent a little time with them. It shouldn’t take long for you to find these same harmonies in new keys once you have the shapes under your fingers. 

Ukulele Lesson: Exploring Your Fretboard with Thirds and Sixths music notation

This lesson is basically a reference guide for thirds and sixths using every possible combination of strings in the keys of F and C major, but I hope you’ll explore them musically and use just what you need a little at a time. Whether you like to play folk, pop, rock, jazz, or mariachi, this little group of shapes is a magical path to great harmonies. You can use them to stack on top of melodies, create slick transitions between chords, or even spice up your solos. Happy double-stopping!

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