Looking for a lesson explaining what are I-IV-V


I am coming back after long hiatus to learning guitar and I recall watching a lesson where Justin explains what do the I-IV-V mean in a chord progression.

For the life of me I cant find it, would anyone be so kind and link it up, please?


Hi Capsel and welcome

Not sure which lesson you are referring to but the I IV V are the Major Chords found in the Major scale. Each scale will have what is called diatonic chords which are based on each interval of the scale and are written in Roman numerals. Each interval represent the root of its diatonic chord.

I ii iii IV V vi viio

The upper case are Major chords the lower case minor and the vii is diminished (o)

So in the key of C (scale note C D E F G A B) the chords would be

C Dm Em F G Am Bdim

For example a standard 12 bar blues is based on the I IV V chords, regardless of the Key.
So in A that would be A D E.

Hope that helps.




That would be in the Music Theory Course, probably in Modules 3 and 4.

This isn’t free content, as it’s part of Justin’s Music Theory course which is paid content.



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Welcome, Capsel. In the old forum @Richard_close2u developed a wonderful thread explaining the Circle of Fifths. The I, IV, V progression is discussed often in that thread. I don’t think he has migrated that thread over here yet (search did not find it) but I believe he plans to migrate it in the near future. Stay active here and you will be rewarded.

Check out the lesson “Chords in a Key for Jamming.” It has an explanation of some different chord progressions.

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In a nutshell:

These refer to chords built on the corresponding scale degree for a given key. For example, in the key of C major the major scale is C D E F G A B. The I chord is built off the first note of the scale (C, giving us C-E-G). The IV chord is built off the fourth note of the scale (F, giving us F-A-C). The V chord is built off the fifth note of the scale (G, giving us G-B-D). As noted up-thread, in a major key these chords will always be major chords (and in a minor key they will be minor chords).

The I chord is also called the “tonic.” The IV chord is also called the “subdominant.” The V chord is also called the “dominant.” These terms and concepts are used in functional harmony. Each chord has a “function” within the key. The tonic is “home,” and you will often hear it used at the beginning and end of a song. The dominant “wants to go home:” it introduces strong harmonic tension and gives a feeling of wanting to resolve or return to the tonic. The sub-dominant gives a “leaving home or away from home” kind of feeling that often leads to the dominant.

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Thanks Robert - indeed it will follow along at some point. Thanks for the shout out. :slight_smile:

Hi. I suspect you may be thinking of the I-IV-V with respect to the Blues? If so then this form primarily uses dominant 7th chords so blurs the lines a little regarding music theory. Regardless of the theory, the I-IV-V is the basis of the Blues so if you look at Justin’s Blues specific lessons you will probably find what you are looking for - 3 chords and the truth!