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I've been taking a fairly beginner music expression course and I've recently learned about chord progressions using chords in I, IV, V.

However, I'm aware that most popular music that you would hear on the radio is generally a four-chord song. How is the fourth chord generally determined?

Niko
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  • Note that the first three chords are not always I, IV, and V. *Smells Like Teen Spirit* is i - iv - III - VI (major/minor flavors implied as the actual chords have no thirds). – Todd Wilcox Dec 04 '15 at 19:23

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Adding a fourth chord to a three chord progression consisting of the I - IV and V chords in a major key can serve many purposes.

For one, it can create a more dynamic and more interesting chord progression. A ii (two minor) or iii (three minor) or vi (sixth minor) chord can add tension to the progression which will beg for resolution back to the root or tonic chord - thereby creating a push pull effect of tension and resolution. A minor chord in a major key progression can serve to lead you to one of the other major chords or serve as a pivot point to switch the order of the progression. These are just some examples of how one of the minor chords can be used in a four chord progression in a major key.

Many possible 4th chords are available including the ii, iii, or vi. You can also use a diminished 7th degree chord or even a flattened 7th degree major chord. Extensions can also be used (7th, 9th, augmented, suspended).

One very commonly used fourth chord in a four chord progression is the vi chord and a popular progression is the I-V-vi-IV progression. Some of the reasons the iv chord is often used as the fourth chord can be found in the answers to this question Why is the I-V-vi-IV chord progression so popular

Ultimately the fourth chord you use depends on what purpose you want it to serve in your song and what you want to accomplish by using it.

A comprehensive online search may yield some helpful guides such as the charts pictured below. As a disclaimer, these charts are merely examples of devices that have been invented to simplify the process of choosing chords and don't purport to offer every possible solution and should not be treated as rules that cannot be broken. Ultimately your goal should be to develop the ability to effectively use your own creativity (guided by music and chord theory) to compose chord progressions that help you express your own personal musical ideas.

Chords for Major Keys

Chord Ladder

Chord Progression Map

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Rockin Cowboy
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  • If a song begins on an upbeat it is likely that the progression will start on the dominant. – Neil Meyer Nov 30 '15 at 09:00
  • Arguably the most used 4 chord sequence is I- vi- IV- V. There must be hundreds if not thousands. – Tim Nov 30 '15 at 18:05
  • @NeilMeyer - if the song begins on the upbeat, it's an anacrucis, and the actual progression starts on the tonic, which is the norm. – Tim Nov 30 '15 at 18:06
  • @Tim or some variation of the I-vi-IV-V. The progression in the popular Axis of Awesome routine is the I-V-vi-IV variation (which is what I meant to say in my answer so I edited to correct the typo). But regardless of the variation, it is true that the vi seems to be one of the most common fourth chords used - and yes its thousands of songs to be sure. – Rockin Cowboy Nov 30 '15 at 18:37
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    @RockinCowboy - With due respect, your pictures / graphs are quite silly; the tension -> resolution ladder is quite incorrect: there is *no way* a "iii" chord is to be considered a "tense" chord. In your chord progression graph, it illustrates that IV cannot go to "vi", which is insane, since that movement offers incredibly smooth voice-leading and is actually very common to hear in music. It doesn't show how "ii" can substitute IV or how "vi" can substitute I, and omits the seven-diminished chord entirely. Apart from showing some major scales, the matrix you provide seems to be incoherent. – jjmusicnotes Dec 01 '15 at 23:43
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    @jjmusicnotes I did not create the charts, I found them & although the ideas suggested are not cast in stone, I personally find them useful. I agree that a IV can go to a vi so the word "rules" in the instructions should be "suggestions". If you follow the "suggestions", you will have a chord progression that works. But you could certainly deviate from the suggestions and still have a chord progression that works. The OP is a beginner so just offering some cheat sheets. The charts are designed to be simple & not cover every possibility. I personally feel a iii chord creates tension. – Rockin Cowboy Dec 02 '15 at 00:01
  • @jjmusicnotes My impression is that none of the charts are meant to represent all the possibilities or be restrictive. Instead, they seem to be showing some basic concepts. There's no way the "Chord Progression Map" could be completed in the sense of having all the possibilities. Perhaps Rockin Cowboy could have disclaimed the completeness of the images to be totally clear, but they are presented "to help with some ideas" and not to be a complete picture of any aspect of music theory. +1 – Todd Wilcox Dec 04 '15 at 19:18
  • @ToddWilcox I understand. My issue is not with whether or not the charts are comprehensive, but that they are omitting some basic, coherent, factually accurate information. I made my comment because I felt the charts took away from Rockin's answer. I'm all for visuals, but we need to make sure we use / show the best information available, not merely what may be convenient. – jjmusicnotes Dec 05 '15 at 02:26
  • @jjmusicnotes Based on your comments I edited my answer (changed the paragraph preceding the charts). I do appreciate your suggestions. My goal whenever I provide an answer on this site, is to provide valuable and useful and accurate content for the benefit of future readers (as well as the OP). I respect your comprehensive knowledge on music theory in general. Your assistance in helping with the accuracy of any of my answers is always welcome! – Rockin Cowboy Dec 05 '15 at 19:48
  • @ToddWilcox I followed your advice to add the disclaimer and edited my answer accordingly. Sometimes I think we write answers without considering all the possible ways they might be interpreted. And I think if we made our answers long enough to cover every conceivable interpretation, we would lose the reader. – Rockin Cowboy Dec 05 '15 at 19:51
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Not necessarily so. There is an awful lot of 3 chord songs (and a lot of awful 3 chord songs, but that's just a joke) that work very well. If a fourth chord is deemed needed, it will usually be one of the following. A minor belonging to the same key, as in ii, iii or vi. The vi is probably the most prevalent of these. Followed by ii then iii. But it will depend on the song. Any extra chord will have to match the notes in the melody. That's just what any chord does. The next option is the dominant chord which leads to the dominant of the key - II. Thus, in C, the missing chord , apart from C, F and G, would be either Am, Dm, or Em, or D(7).

Other options in general use could include I7, to move to IV, and iv (minor F in C) to get back to I. There's maybe a list of probable chords, in usage order, to consult. In fact, it may be an interesting exercise to compile such a list from popular song chord make ups that does this. It'd probably go I, V, IV, vi...

Tim
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    To clean up some of your points concerning music theory - the dominant of a key is the V chord, not a II, which would be a V/V a.k.a a secondary dominant. You would never label a "I" chord as a "I7", but rather a V7/IV - you need to show functional relationship when present. You're correct on both counts about three-chord songs, but you miss the mark in answering the OP's question. In a four-chord progression, the last chord is very, very typically going to be a IV, V, or secondary dominant. Use of a "vi" or "ii" typically serve as substitutions of I, IV, and V to prolong the *middle*. – jjmusicnotes Nov 29 '15 at 21:41
  • @jjmusicnotes - thank you for the guidance, much appreciated.What I tried to portray was the dominant chord leading to the dominant of the key. Thus, in C maj., (dominant G), it would be D (or D7). If I call a chord V7/IV, then yes, it's the dominant 7th leading to the subdominant, which is where most dominants go - up a fourth. My glitch is if I see V7/IV, and I'm reading it live, I see the V7 first, and automatically go to D7 in C. II may not be technically correct, but it helps me play the right thing! The 'fourth chord' (O.P.) I took to mean the next most used chord after I, IV and V. – Tim Nov 30 '15 at 09:02
  • @jjmusicnotes - where does that leave Sweet Georgia Brown? In G, goes E - A - D - G chordally. So given G=I, that could make E technically V/V/V - rather unwieldy. And the B7 in there would be V/V/V/V. Help! – Tim Nov 30 '15 at 09:05
  • Thanks for explaining how you interpreted the OP's question about the "fourth chord", I obviously took it to mean the fourth chord of a sequence. Regarding Sweet Georgia Brown, if the chords are functioning as secondary dominants, then yes, V/V/V or V/V/V/V would be absolutely right, even if it seems silly / stupid. I've analyzed Beethoven string quartets that had a similar train of secondary leading-tone chords, as well as non-functional secondary dominants (such a rebel!). Yes, you'll feel stupid writing that many "V's", but it's correct. :) – jjmusicnotes Nov 30 '15 at 23:44
  • @jjmusicnotes - thanks again. Some of these rules were made by non-musos, I guess! Incidentally, in my first comment, I should have said 'In C, if I see V7/IV, I automatically go to G7, not D7. A sort of N.N.S. I prefer and have adapted. – Tim Dec 01 '15 at 08:13
  • No problem. For what it's worth, in your defense, people typically don't read roman numeral analysis "live" unless they are sight-reading figured bass realizations in a Baroque ensemble. If you're playing in a rock band, I'd suggest just putting pop chord symbols in and not worrying about showing the functional harmony. – jjmusicnotes Dec 01 '15 at 23:36
  • @jjmusicnotes - yes, it's pretty well like reading Nashville number system, except with Roman numerals instead of Arabic numbers. I find the latter not so clear, so my way works for me. It's not analysis per se, but an easy way to be able to play a song in any key, rather than reading iin Eb, say, and changing it on the fly to F#. So in these cases, in C, D7 would be written as II7, as it's not contravening any rules. Whilst playing a song, I don't need to know whether it's a secondary dominant, etc., only what I need to play. – Tim Dec 02 '15 at 09:09