Diatonic 3rds are intervals of a third built from the notes of a major or minor scale, and they are played either melodically (one note after the other) or harmonically (both notes at once). Below are guitar tabs for both approaches in G major, plus the theory and practical tips to use them in your own playing.
What Are Diatonic 3rds?
A diatonic 3rd is the interval between a scale degree and the note two scale steps above or below it, staying within the scale’s seven notes. For example, in G major (G A B C D E F#), the 3rd above G is B, above A is C, above B is D, and so on. The interval is major or minor depending on the scale degrees: in a major scale, the 3rds alternate between major (on degrees 1, 4, 5) and minor (on degrees 2, 3, 6), with a diminished 3rd on the 7th degree (F# to A is actually a minor 3rd, but F# to A is a minor 3rd; the 7th degree’s 3rd is diminished only if you consider the 7th as the root of a diminished triad – in practice, the 3rd above the 7th is minor).
This pattern of major and minor 3rds is what gives diatonic harmony its characteristic sound. When you play two notes a 3rd apart, you are outlining a chord fragment – the root and 3rd, or 3rd and 5th – which is why 3rds are so common in melodies and harmonies.
Melodic 3rds – Guitar Tabs in G Major
Melodic 3rds are played as successive notes, usually ascending or descending the scale in 3rds. The most common way is to play the lower note of each 3rd, then the upper note, then move to the next scale degree and repeat. Here is a two-octave pattern in G major, starting on the 3rd fret of the low E string (G).
G Major Melodic 3rds (ascending, two octaves) – standard tuning
e|------------------------------------------------------------------------|
B|------------------------------------------------------------------------|
G|------------------------------------------------------------------------|
D|------------------------------------------------------------------------|
A|------------------------------------------------------------------------|
E|--3--3--5--5--7--7--8--8--7--7--5--5--3--3--2--2--| (then back down)
G B A C B D C E D B C A B G A F#
But that tab only shows the lower notes. A proper melodic 3rds exercise plays both notes of each interval, like this:
G Major Melodic 3rds (ascending, one octave) – play each pair as two notes
e|------------------------------------------------------------------------|
B|------------------------------------------------------------------------|
G|------------------------------------------------------------------------|
D|------------------------------------------------------------------------|
A|------------------------------------------------------------------------|
E|--3--3--5--5--7--7--8--8--| (lower notes: G A B C)
D|------------------------------------------------------------------------|
A|------------------------------------------------------------------------|
E|------------------------------------------------------------------------|
B|--3--3--5--5--7--7--8--8--| (upper notes: B C D E)
e|------------------------------------------------------------------------|
Actually, the standard way to notate melodic 3rds is to show both notes on a single staff, with stems indicating which is played first. On guitar, you can play them on adjacent strings. Here is a practical tab for G major melodic 3rds on the top three strings, ascending from G (3rd fret, high E) to B (7th fret, high E):
e|--3--3--5--5--7--7--8--8--| (upper notes: G A B C)
B|--3--3--5--5--7--7--8--8--| (lower notes: E F# G A – wait, that's not right)
G|--------------------------|
Let me give you a correct, playable tab. The most common melodic 3rds exercise uses the G major scale on the D and G strings, or G and B strings. Here is a clean one-octave ascending pattern on the D and G strings:
G Major Melodic 3rds (ascending) – D and G strings
D|--3--3--5--5--7--7--8--8--| (lower notes: G A B C)
G|--3--3--5--5--7--7--8--8--| (upper notes: B C D E)
Play each pair as: G-B, A-C, B-D, C-E.
To play it, pick the lower note (D string) then the upper note (G string) for each pair, then move to the next pair. This creates a smooth, scale-like melody that outlines the underlying chords.
Harmonic 3rds – Guitar Tabs in G Major
Harmonic 3rds are played simultaneously – you pick both notes at once. On guitar, this is usually done on adjacent strings, often with a barre or a finger per note. Here is a G major harmonic 3rds exercise on the D and G strings, ascending one octave:
G Major Harmonic 3rds (ascending) – D and G strings
D|--3--5--7--8--| (lower notes: G A B C)
G|--3--5--7--8--| (upper notes: B C D E)
Play both strings together for each fret pair.
But wait – that tab is wrong because the frets are the same on both strings, which gives a unison, not a 3rd. For a 3rd, the upper note must be two scale steps higher, so the frets will differ. Here is the correct tab:
G Major Harmonic 3rds (ascending) – D and G strings
D|--3--5--7--8--| (lower notes: G A B C)
G|--4--5--7--9--| (upper notes: B C D E – wait, B is 4th fret on G, C is 5th, D is 7th, E is 9th)
Play both strings together.
Let me verify: On the G string (3rd string), the notes are: open G is 0, fret 2 is A, fret 4 is B, fret 5 is C, fret 7 is D, fret 9 is E. So for G-B, you play D string fret 3 (G) and G string fret 4 (B). For A-C, D string fret 5 (A) and G string fret 5 (C). For B-D, D string fret 7 (B) and G string fret 7 (D). For C-E, D string fret 8 (C) and G string fret 9 (E). So the correct tab is:
G Major Harmonic 3rds (ascending) – D and G strings
D|--3--5--7--8--|
G|--4--5--7--9--|
Play both notes together.
This produces the intervals G-B (major 3rd), A-C (minor 3rd), B-D (minor 3rd), C-E (major 3rd). You can continue up the scale: D-F# (D string fret 10, G string fret 11), E-G (D string fret 12, G string fret 12 – but that’s a unison? No, E to G is a minor 3rd, so D string fret 12 (E) and G string fret 12 (G) – that’s correct because G is on the 12th fret of the G string).
How to Practice Diatonic 3rds on Guitar
Start slowly with a metronome, and use the following steps:
- Learn the scale first: Play the G major scale in one position until you can find any note without thinking.
- Play melodic 3rds on one string pair: Use the D and G strings, pick each note separately, and say the interval (major or minor) out loud.
- Add the second string pair: Once comfortable, move to the G and B strings, then the A and D strings.
- Switch to harmonic 3rds: Use the same fret patterns but pick both strings at once with a slight rake.
- Move to other keys: Use a capo or shift the pattern up the neck to play in other keys, but remember the pattern changes because of the B string tuning (the B string is tuned a major 3rd above G, not a perfect 4th).
Common Mistakes and How to Avoid Them
One common mistake is playing the same fret on both strings, which gives a unison or an octave, not a 3rd. Another is forgetting that the B string breaks the pattern – when you cross from the G string to the B string, the fret numbers shift by one because of the tuning. For example, a 3rd that is frets 3 and 4 on D-G becomes frets 3 and 5 on G-B. Always double-check the notes, not just the frets.
Another issue is muting adjacent strings. When playing harmonic 3rds, you may accidentally hit the string between the two you intend. Use your picking hand to lightly rest on the unused strings, or use your fretting fingers to mute them.
Using Diatonic 3rds in Songs and Solos
Diatonic 3rds are a staple of rock, blues, and country guitar. Think of the intro to “Sweet Child O’ Mine” – that’s not 3rds, but the solo uses them. More directly, the Allman Brothers’ “Jessica” and many Lynyrd Skynyrd solos use melodic 3rds. In a solo, you can play a melody in 3rds to add richness – instead of playing a single note, double it with the note a 3rd above (or below) from the same scale. This works especially well over a static chord or a slow progression.
For example, over a G major chord, you can play G-B, A-C, B-D, C-E, D-F#, E-G, F#-A – all diatonic. Over a C major chord, use the C major scale’s 3rds: C-E, D-F, E-G, F-A, G-B, A-C, B-D.
Alternatives to Diatonic 3rds
If you want a different color, try:
- Chromatic 3rds: Move every note by a half-step, regardless of key – gives a tense, outside sound.
- 6ths: Invert the 3rd – play the lower note a 6th below the upper, which is the same as a 3rd but with a wider spread.
- Octaves: Double the melody an octave up or down – simpler and very common.
- 4ths or 5ths: More open, modal sound.
Frequently Asked Questions
What’s the difference between melodic and harmonic 3rds?
Melodic 3rds are played as two separate notes in sequence – you hear the interval horizontally. Harmonic 3rds are played together as a chord – you hear the interval vertically. Both use the same notes, but the texture and feel are completely different.
Do I need to know music theory to use diatonic 3rds?
Not strictly – you can learn the fretboard patterns by rote. But understanding which 3rds are major or minor helps you improvise and transpose to other keys. It also lets you avoid hitting a wrong note when the chord changes.
Why does the pattern change when I cross the B string?
Because the guitar is tuned in mostly perfect 4ths, but the G-to-B strings are a major 3rd apart. That means the same interval (e.g., a major 3rd) will have a different fret spacing on that string pair. You have to adjust your fingerings – usually by moving the upper note one fret higher than you would expect.
Can I play diatonic 3rds in minor keys?
Yes, and it’s often even more expressive. In a natural minor scale, the 3rds are minor on the 1st, 4th, and 5th degrees, and major on the 3rd, 6th, and 7th. The pattern is the same as the relative major scale – for example, E minor uses the same notes as G major, so the 3rds are identical.
What are some famous songs that use diatonic 3rds?
Many classic rock and blues solos use them. “Free Bird” by Lynyrd Skynyrd has a section with melodic 3rds. The Eagles’ “Hotel California” solo uses them too. In country, almost every Telecaster player uses 3rds – think of Don Rich or Albert Lee.
Should I practice 3rds with a metronome?
Yes, especially when you start. Set the metronome to a slow tempo (60-80 BPM) and play each 3rd as a pair of eighth notes. As you get comfortable, increase the speed. Metronome practice ensures even timing and helps you internalize the intervals.
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