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It's like I see I IV V chords everywhere. No matter what song I play, or what key I'm in, they're always there. I also noticed that the circle of fifths is made out of fifths (clockwise) and fourths (counter-clockwise). And correct me if I'm wrong, but I think the circle of fifths is the most important diagram of music.

So yeah the I IV V are everywhere. I can't escape it. Is it some kind of best kept secret in music or something? Does music revolve around these chords, or am I losing my mind?

marked as duplicate by Richard, Doktor Mayhem May 8 '17 at 6:31

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    It really depends on the genre of music that we're talking about here. In the Classical tradition, yes, they're everywhere. However, let's say we're talking about certain EDM sub-genres like Trap music, then they're nowhere to be seen. These genres tend to be more modal in nature, meaning that the I chord is not "home base", rather the iii, ii or vi chord may be home base making the composition Phrygian, Dorian or Aeolian respectively. – 02fentym May 7 '17 at 1:47
  • yes I'm talking about mainly pop songs, rock songs, traditional songs, folk songs, christmas songs, disney songs, classical, etc. So mainly what the general western culture perceives as "familiar". – foreyez May 7 '17 at 1:53
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    Are they used all the time? Absolutely. But whether they're "the heart of music and harmony" is subjective. – Richard May 7 '17 at 2:12
  • You are seeing them all the time because you are only looking at music that uses them all the time. You won't find many here, for example: youtube.com/watch?v=-HDY6Dvegu8 – user19146 May 7 '17 at 3:11
  • True, they are used all the time. But that isn't any reason why they're used in most children's songs, specifically, so this is hardly a duplicate. – Tim May 8 '17 at 7:12
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It's not a secret. The I, IV, and V chords are the primary triads. The three chords as a set include all the diatonic tones. So, it is possible to harmonize any diatonic melody with only these three chords.

Also, the circle of fifths is another music theory fundamental. But, you should take some time to look into how it is used as both a key signature diagram (see this cheat sheet and this Wikipedia article) and a harmony tool. The circle of fifths is often used to describe harmony, but I prefer to think of root progression by descending fifth and use the circle as a key signature diagram. Consider that the very common harmonic sequence I-IV-viio-iii-vi-ii-V-I is not part of the circle of fifths! I think of root progression and sequences for harmony rather than the circle of fifths.

The distinction is the circle of fifth key signature diagram uses all perfect fifths while the harmonic sequence of descending fifths is diatonic and includes a diminished fifth at IV-viio. Keep in mind if you move two or more places on the circle of fifths key signature diagram - while thinking of the key names as chord names - you will get chromatic chords outside of the key. Example: C to F to Bb, the Bb major chord isn't in the key of C major. Whereas in the diatonic sequence the chords are I-IV-viio or chords of C major - F major - B (natural) diminished. Just be aware one is chromatic and the other is diatonic.

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Using I, IV and V

I, IV and V are the building blocks of most of the genres that you mentioned up in the question's comment section. They encompass all of the notes of a scale, making them very versatile when matching chords to a melody.

Usually, if the song begins on the I chord, then the song will also end on the I chord. Ending on the I chord brings a great level of stability to the end of a musical phrase. Let's say we have a 4-bar phrase where each bar has a single chord (4 beats each).

Chord 1: I
Chord 2: IV
Chord 3: V
Chord 4: I

If we play these chords in succession, finishing off the phrase with the I chord brings us back "home" (to a point of stability). Contrasting this idea is the following phrase:

Chord 1: I
Chord 2: IV
Chord 3: V
Chord 4: vi

In this example, the phrase can feel incomplete since we didn't finish it off with the I chord.

Music does not have to revolve around these chords though. As I was saying in the comment section, there are other genres of music that do not use the I to provide stability to a phrase. The song "Royals" by Lorde, which was popular a few years back has the chords V, V, IV, I. Notice how the song begins on the V chord. It's the V chord that actually brings a sense of stability in this song and this makes the song modal, specifically of the Mixolydian mode. The Mixolydian mode begins on the 5th note of a major scale. For example in the Lordes song, they are in D Mixolydian is D E F# GA B C D ... At first glance it's the same as G major, but it's usage is very different.

Cycle of Fifths

This is a very important concept. It is commonly seen as the cycle of 4ths since it is written as C F Bb Eb Ab Db Gb/F# B E A D G C ..., but it is definitely a series of 5ths. The reason is because of the relationship between noten and noten+1. The first note C is the 5th note of the key of F major. They share a V to I relationship. The same is true for F and Bb. F is the V in Bb major. And so on and so forth.

There are some practical uses for the cycle of fifths that go beyond the scope of this question, but I'll list them:

1) Chord Substitutions
2) Chord Insertion (sticking an extra chord or chords in between existing chords in a song)
3) etc...

  • 'Sweet Home Alabama' is similar in that it has V-IV-I structure, although some say it's in the key of its first chord. Cycle of 4ths/5ths is just one way or the other. C>G=5, G>C=4. Same difference. – Tim May 7 '17 at 4:34
  • Yup, "Sweet Home Alabama" is mixolydian in that case. If you say that it's in the key of the first chord, that's fine, but then you have to deal with the second chord as a bVII chord. To each his own. – 02fentym May 7 '17 at 4:38
  • I have this sort of conversation whenever I play it in a different band. Some finish on I, some insist on V. Even the Allman Bros. did it both ways! To me it only sounds finished on its 3rd chord in the sequence - but that's often my problem with modal stuff - it gravitates to its parent key... – Tim May 7 '17 at 4:46
  • I hear you. When I play with my band, I would call the key C and not G mix just so that we don't have to renumber all of the chords...it's just too awkward. I mean, you'd literally have 7x12 numeric patterns if you did that...it's unmanageable. – 02fentym May 7 '17 at 5:50
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    Although (as mentioned in the above comments) it is possible to see mixolydian as a tonality that is centred around the V degree of a major scale, that seems to be an unusual way of thinking about it these days. Much more commonly I see mixolydian explained as being built on the V degree of a major scale, but with that note then becoming the I of the new (mixolydian) tonality. – topo morto May 7 '17 at 6:40
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Take that circle/cycle of 4ths/5ths. Stop at any point. The two neighbours, either side, are the IV and V of the I. So it's hardly surprising that those 3 become the mainstay of a lot of Western (at least) music.

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If you play cowboy songs, you'll hear a lot of I, IV, V, I. The slightly more developed version - which demonstrates the 'cycle of 5ths' basis of the progression rather more clearly - is I, ii7, V7, I. You'll also hear a lot of I, vi, IV, V, I. If you move away from the campfire to the coffee shop (or the teenage bedroom) you'll start hearing vaguely modal Em, Dm, C then an argument over whether to play Bm or B7 :-)

Then you could get out MUCH more...

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