Part 2: I analyzed the chords of 1300 popular songs for patterns.

[gnaritas]

> What stands out here, is that IV → I (F to C) is not only normal, it actually shows up just as often as V → I. This is surprising (at least to a classically trained person).

That's not surprising at all, and I don't believe for a second that a classically trained person would think so either. V -> I is a common movement for resolution, so is IV -> I as are several others. While his data is interesting, I find the analysis weak, he's acting surprised at perfectly known and normal things, even to someone classically trained IMHO. IV -> I isn't "breaking the rules".

[dfan]

Agreed, this is definitely not surprising. In fact, one of the biggest broad distinctions between the harmonic rules of classical music and pop music is that classical music tends to use authentic cadences (V -> I) and pop music tends to use plagal cadences (IV -> I). (If you're curious, in jazz the cadence you see all the time is ii7 -> V7 -> I7.) Of course I am speaking in large generalities; there are millions of exceptions.

The canonical classical music harmonic progression is I -> IV -> V -> I, whereas that famous four-chord sequence that underlies hundreds of pop hits pretty much runs the same sequence in reverse: I -> V (-> vi) -> IV -> I.

[msluyter]

Well, as a classically trained musician, I certainly would expect V-I to be much more common than IV-I, as a cadence. (Defining "classical music" as music roughly from 1650-1900ish). But it sounds like the author didn't really limit his analysis to cadences. My impression was that he just counted every chord that precedes a C chord, which even in classical music would include lots of non-cadential IV chords moving to I chords in the interior of phrases. For non-cadential chord progressions, I'd expect IV-I to be fairly common, though it's unclear to me that it'd be more common than V-I. I mean, just the coda of any Beethoven symphony alone would probably skew the stats in favor of V-I, generally. ;) So, I'd like to see the author clarify that.

As for the explanation, I thought it might have something to do with rock's origins in 12-bar blues (I-VI-I-V-I), though I know that pop has moved away from that considerably.

[davec]

I disagree that a classically trained musician wouldn't be surprised at the predominance of IV -> I in popular music. Plagal cadences aren't nearly as common as V->I in the common practice period, and when it is used, the pull of IV to I isn't nearly as strong. The resolution is much weaker.

[kefs]

Relevant:

https://www.youtube.com/watch?v=5pidokakU4I

[pygy_]

The Pachelbel Rant is also worth checking:

http://www.youtube.com/watch?v=JdxkVQy7QLM

[jschulenklopper]

For an interesting visual way to map common chord progressions, also see http://chordmaps.com/mapC.htm for in the key of C. Steve also made a generic one: http://chordmaps.com/genmap.htm.

I have this as a reference on the piano, and it is nice to experiment with several routes to return to the root chord (nicely positioned at the bottom of the page).

[anigbrowl]

This is much better than the first part.

[yathern]

It's nice to see the data, but I must say I V VI IV was not surprising at all. I'm sure it's slightly more 'emotional' cousin VI IV I V (think apologize) is high up on the list.

[slashcom]

Please train a Conditional Random Field on this data. (A hidden markov model would also be interesting, but risks going out of key more easily).