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If you’re learning to play guitar or you’ve played guitar for years and have never dove into music theory, you might be wondering what you should learn and what an experienced guitar player is expected to know. 

Let me start off by saying that there are different types of guitar players out there and the genre of music you play will also be a factor in what is expected in terms of music theory. A Jazz guitar player will generally be expected to know more music theory than a rock and metal guitar player (although all guitar players should know at least the basics, but some genre’s are more academic than others). 

Also, if you are looking to become a professional freelance guitarist, there are more expectations than if you just want to be able to play technique demanding guitar songs. 

For the sake of this article let’s talk in general terms. 

In general, the music theory concepts that guitar players should learn and understand are intervals, scales and modes, chord construction, chord function to create chord progressions, Roman Numeral Analysis, the Circle of Fifths and time signatures, 

Let’s go over each. 


If you’re not already familiar with intervals they are essentially the distance or gaps between two notes. 

For example, in a C minor scale you have C as the first note which is often called the Root note, then the next note in the scale is D, which we call a second because it’s the second note in the scale. 

The D is a full step (rather than a half step) away from the C note. This full step difference between the C and D note is called a Major 2nd interval, because we have names for each interval (the amounts of distances). 

So the distance or gaps between notes is what intervals are, and distances between notes are how scales and chords are constructed. You can see why it’s so important to know and understand them. They form the foundation for all music and music theory. 

Scales and Modes

This is also incredibly important to understand because scales and modes are what you will use to make melodies. So what scales and modes should you know?

You should know:

  • Major scale
  • Minor scale
  • All 7 modes (Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian and Locrian)
  • Pentatonic and Blues scales
  • These are extra credit but get used often: Harmonic Minor and Melodic Minor

In case you don’t know what modes are, they are essentially the moods of music. You can read more about them in this blog post called How to Write Songs Using Modes.

Chord Construction

Once you learn about and understand Intervals and Scales you can learn about how chords are constructed. 

Essentially, you could say that two notes or more being played at the same time form a chord. For example, you could look at powerchords which are made by playing a note that has a perfect 5th interval played on top of it at the same time. 

There are also triad chords and chords with extensions. Triad chords are formed by playing 3 different notes on top of each other. These are the root, 3rd, and 5th notes of a scale. Chords with extensions are chords that have 9th, 11th, and 13th notes. 

If you understand intervals and how chords are made and want to read more about chord extensions check out these two blog posts What Are Chord Extensions? and How to Use Chord Extensions in Songwriting.

Chord Function

This might sound complicated but is actually really simple. It is referring to the role a chord plays in a chord progression. 

If you have a key like C major, you can create chords out of each note of the C major scale. The formula is:

Notes of C Major scale: C, D, E, F, G, A, B, C

Chord qualities: Major, Minor, Minor, Major, Major, Minor, Diminished

C major scale with chord names:

Cmaj, Dmin, Emin, Fmaj, Gmaj, Amin, Bdim

So in the key of Cmaj, some of these chords are going to increase or decrease tension.

With the concept of chord function we give names to the amount of tension they add. These names are:

  • Tonic: the most stable and neutral. This includes the first, third and sixth chords in a scale. 
  • Subdominant: this increases tension slightly. It includes the second and fourth chords. 
  • Dominant: this is the highest amount of tension. It includes the fifth and seventh chords in a scale.

By knowing which chords add or remove tension you can create chord progressions that flow and lead the listener smoothly through tension and release. This is why it’s important for guitar players to understand chord function. It’s one of the most important things to understand if you want to know how to make beautiful, flowing chord progressions. 

If this is something that interests you check out this blog post that goes deeper into this topic called Chord Function: The Compass to Flowing Chord Progressions.

Roman Numeral Analysis or the Nashville Number System

There’s basically two names for this. You can call it Roman Numeral Analysis if you’re using Roman numerals or the Nashville Number System if you’re using regular numbers (1, 2, 3 etc)

Though this might sound like the Dewey Decimal System which libraries use to organize books, this is something completely different. 

Essentially it’s a shorthand way to write down chord charts instead of reading sheet music. Like slang, but for sheet music. 

The idea is to assign Roman numerals to each chord in a key. Then when you have a song with a chord progression you could just say what the song’s key is and write down the number assigned to each chord in the progression. 

So if a song was in C major and the chords were Cmaj, Gmaj, Amin, Fmaj

Musicians could instead write them down like this: Key – Cmaj, Progression: I, V, vi, IV.

This helps avoid having to learn individual chords for songs. It’s easier to remember the numbers. It also makes it easier to move the progression to different keys.

As you can see most are uppercase Roman numerals but the vi is lowercase. That is because uppercase means it’s a major chord and lowercase means it’s a minor chord. Here is the Cmaj  key in Roman Numerals:

I, ii, iii, IV, V, vi, VII°

Cmaj, Dmin, Emin, Fmaj, Gmaj, Amin, Bdim

Circle of Fifths

Aside from looking like some kind of medieval satanic sigil, the Circle of Fifths is also really useful for seeing the relationships between different scales and chords.

It can help you 

  • Easily find what the relative minor chord is to a major chord.
  • Easily see what the IV and V chords are relative to the I or tonic chord.
  • Find which chords work together in a key to create chord progressions.
  • It can help you jam with people on the fly where they might say let’s do a I, V, vi, IV in the key of Cmaj, you can visualize the Circle of Fifths diagram and easily know what chords those are.
  • It can help you find borrowed chords from other keys or find secondary dominant chords which helps to spice up your chord progressions. Here’s an article about 5 Ways Songwriters Spice Up Boring Chord Progressions.

So as you can see there are a lot of applications for this and especially when things are being done on the fly, this can be really useful. 

Time Signatures

Another basic concept guitarists need to understand is time signatures. It is how we divide time in music when we write it down into sheet music. Rhythm is all about this. 

The technical definition for time signatures is it’s the music notation used to specify how many beats of a particular note value are contained in each bar or measure. So how many beats in one measure, and what beat duration do we consider to be one beat.

This is important for guitar players to understand because it governs the rhythm of their playing. It will tell you how much time you have in each measure to do a rhythm with your guitar playing before repeating the phrase over again. 

Time signatures can be very simple and get more complex. The simplest and most common time signatures are 4/4 and 3/4. These are very steady pulses and are straightforward-sounding. 

They can also get more complex by using odd number time signatures such as 5/4 or 7/8. The feeling of time signatures like these are like there is an extra beat or like a beat was skipped before repeating the phrase. It’s like a stumbly feeling. These are more advanced so for now just deal with 4/4 and 3/4 and move on to the odd time signatures later. 

Recommended Books

There are many books out there that can be excellent aids in helping you learn this stuff. However, some very popular ones amongst guitar players that serve as great references are the below.

The Guitar Grimoire:

Scales and Modes

The Guitar Grimoire:

Chords and Voicings

The Guitar Grimoire:

Progressions and Improvisation

Additional Questions About Music Theory for Guitar Players

Here are answers to a few additional questions you may have. 

Do you need to know music theory to be a good guitarist?

You can be a good guitar player without knowing any music theory if you have a good ear and a talent for technique required to play the instrument. However, if your goal is to become a good professional freelance guitar player, you should know at least the basics of music theory to allow you to communicate and work with other musicians.

You also need to consider the genre of music you want to play. If you play jazz you will be expected to know more music theory, whereas if you play something like rock and metal you might not be expected to know much music theory at all, even at professional levels. 

Just look at Dave Grohl who admits he does not know music theory yet has played the worlds biggest venues, arenas and stadiums with Foo Fighters and is considered a rock god. Of course I’m sure he knows at least the basics like how to play different chords and scales. 

Will music theory make me a better guitarist?

Yes because it will help you be more well rounded in your abilities and help you know what you can do in different situations. 

In addition, it will make you a lot easier to work with when you’re engaging with other musicians, especially during songwriting and improvisation. 

For example, if you have to solo, knowing the modes will give you more options than just knowing the minor, major, and pentatonic scales. Also if you’re writing a song on guitar and there is a chord in a chord progression that you don’t like, knowing music theory will help you know what other chords you could switch for that one to make it more interesting. 

In what order should I learn music theory for guitar?

Guitar players looking to learn music theory should learn the following concepts in this order: intervals, scales and modes, chord construction, chord function to create chord progressions, Roman Numeral Analysis, the Circle of Fifths and time signatures,

Do I need to know music theory to write a song on guitar? 

To write songs on guitar you don’t need much music theory knowledge, but should be well acquainted with the basics and know some basic chords and scales. 

What is great about songwriting is that if you have a good ear, you can get by with knowing the bare minimum. You don’t need to know how music theory works to use chords and scales if you have a good ear. 

That being said, the more music theory you know the better. It really helps to know your options. 

Wrapping It Up

As you can see there is not a lot of music theory that most guitar players will need to know to start doing some pretty amazing things. It really is a matter of being creative and applying what you learn, even if it’s not a lot right now. 

Keep in mind I kept this pretty general too. This will help you survive in most situations but I’ve known people that don’t know any of these things and just have an incredible ear and talent or they practice technique so much that they can do complex things even though they don’t completely understand what they are doing theory-wise. 

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