If you start at the 1950s, you'll see very simple rock songs; your classic three-chord rock songs. As you hit the 1960s you'll see more complexity; The Beatles, for instance, had more harmonic complexity than what had come before, which continues to be imitated into the 1970s. Then what happens? I don't know, by the 1980s you're looking at a lot of very simple music again, though music is becoming more diverse genre-wise so you're probably getting a larger spread. Then by the present day you have a disturbing trend of one-chord or even no-chord music; apart from rap [which contains no singing but seems to have got simpler even in the backing tracks over the years] we now find that even sung songs are completely lacking in harmony or chord progression. A particularly annoying example I noticed the other day would be that song (dunno who it's by) with the lyrics "We found love in a hopeless place", which seems to have a melody of just four notes.
I could continue this discussion going backwards in time from the 1950s and talking about how the ever-growing harmonic sophistication of art music through Beethoven to Wagner eventually led to a complete breakdown of the idea of harmony in art music which led to music that nobody liked which led to the death of art music and the establishment of rock and roll from square one, but that's another discussion.
http://www.icce.rug.nl/~soundscapes/DATABASES/AWP/awp-notes_...
They were originally Usenet postings(!) starting in 1989 or thereabouts, but have been revised a bit. Warning: you could lose hours reading through them all.
One thing that comes up many times there that I'd be interested in seeing added to a quantitative analysis like this one is how many times something can "seem" like it might be in one key but ends up really being in another, but I don't know how you would count that.
You also have to be careful because Bach and Purcell didn't think in terms of our modern harmonic structure. They worked in voicing and figured base, which produces similar, but not identical, results. Go back a little farther, and it's all voicing. Palestrina in in some ways closer to Schoenberg than Haydn.
As for the breakdown of harmony in art music, not so much. Serialism got all the academic and theoretical attention, and many mediocre composers with a theoretical bent worked in it, and a few great composers like Stravinsky and Shostakovitch, but it's hardly all the art music that was being composed. Many composers got through their whole careers without any particular use of it, such as Walter Piston. What that has to do with rock and roll is a mystery to me, since it's an offshoot of jazz, which is alive and well and still serving as a wellspring for new music.
Also, using harmonic progression alone as a measure of musical complexity or richness is misguided. Steve Reich's Violin Phase contains only 5 notes, but was a seminal piece of minimalist music in the 1960s:
http://grooveshark.com/#!/s/Violin+Phase/3nPoC4?src=5
Musical richness can come from a lot of places. Hip-hop, as a genre, tends to focus on rhythmic texture and narative content. I'd say, on average, pop hip-hop these days is richer than pop rock. There's also some really great stuff that's come out of the hip-hop world, depending on how far away from pop you're willing to still call something hip-hop, e.g. DJ Spooky:
http://grooveshark.com/#!/s/Peace+In+Zaire/2UyeL0?src=5
Just as an example, I love the texture of a lot of stuff from The Roots:
http://grooveshark.com/#!/s/Don+t+Feel+Right/2LzmSC?src=5
(Note: Several members of The Roots are competent jazz musicians.)
Even Miles Davis's most known albums, Kind of Blue and E.S.P. represented a step towards more simplisitic harmony – "modal jazz" – far simpler than the hard-bop which was at the time prevalent and which Miles had previously played.
The assertation that harmonic complexity precluded the death of art music also seems off-base. Art music was always high-falutin' stuff that mostly rich people, or those wanting to emulate them, listened to. The rise of the relative importance of pop music had more to do with the invention of the phonograph than the increase in harmonic complexity. In fact, many of the first post-romantic composers, Satie, Debussy and Ives, tended towards more simplistic harmonies (arranged in ways that violated the rules of classical and romantic functionalism). It wasn't until the modern period, well after the rise of recorded pop music, that harmonies got particularly wild.
There was a Cambrian explosion of music in that period, and virtually no one ever heard of 90%, probably 99%, of the bands. Countless groups sprang up all over the place and pressed records for their local markets. People have devoted careers to tracking down the recordings of that period; one of them, Greg Shaw (whom I knew for a while) had over a million records. He put out a series of influential compilation albums of his favorites that spawned an entire genre (garage rock). Decades later, this stuff is still being unearthed and released. There are entire series of albums devoted to the 1960s proto-punk of Oregon, or Denmark, or Uruguay. It's just amazing how much there is (enough that I'm skeptical of claims that more was recorded in the 80s), and much of it -- tastes vary, of course -- remains amazingly alive and good. A lot of people would disagree that it hasn't stood the test of time; every generation produces new acts in this lineage (e.g. Black Keys), and the underground history of the music continues to be handed down through the fanbase. Its popularity ebbs and flows in a 10-year cycle or so. Right now it's on an upswing.
Edit (by way of response to the rest of this thread, not to your comment): it's foolish to identify complexity with good music. Punk/new wave was a reaction against complicated, highly produced music which used an awful lot of chords. The entire career of bands like the Stooges and the Ramones was a self-conscious mining of the opposite aesthetic. Consider the famous 2-note guitar solo in the Buzzcocks' "Boredom": http://www.youtube.com/watch?v=QoYiQ8Qsozk&t=1m19s. The rest of the band was rolling on the studio floor laughing while the guitarist played it because nobody believed it was possible to do a guitar solo like that, let alone for that long. It's as far from complicated as you can get but still a great creation. Or think of John Cale's one-note piano drone that runs through the Stooges' "I Wanna Be Your Dog": https://www.youtube.com/watch?v=3gsWt7ey6bo#t=23. Cale came from La Monte Young and the Fluxus movement -- highly self-aware avant garde early 60s stuff that he put into a deliberately primitive incarnation. Not saying everyone should like it, but it's as influential and artistic as anything of the last 40 years.
The only rule is that you can't predict what form great art will take. The minute somebody thinks they've figured it out (number of chords? please), the muses jump and bless the opposite.
It's by Rihanna, and I can't even understand how it got released. It's like something that got rejected from how-to-make-techno.tumblr.com for being too basic.
I've always wanted to take the lyrics of popular songs and run them through a Markov Chain, just to see what could get produced. Ultimate goal would be to generate a song, the lyrics and then have users upload videos of themselves singing it out.
I might argue that the regression towards simpler music starting in the 1980s might be due to MTV and increased media coverage of music stars. Starting with MTV and music videos, to be really successful, your looks started to matter. This gave rise to acts who may not have been as musically talented, but were more marketable because they looked better on TV. That's not to say that music acts were never on TV before 1980, which is obviously not true, but MTV did change the game quite a bit and maybe started this trend of towards simpler music with prettier stars.
It's not that art music has had a big fall from grace and lost its grip on the public's heart, paving the way for rock and pop. It never had that grip in the first place. The musical descendants of Bach and Beethoven are alive and kicking; just look at John Williams.
You could point to the Neo-Classicists -- although Prokofiev's dead, of course. Or there's Penderecki; perhaps a hard sell, but deserving.
Do you mean 'rock songs' as in Jimmy Preston's Rock the Joint? Or do you mean 'rock songs' as in rhythm and blues/'black music'/music made by black people? If you mean--well, there is no other way of putting this--music that white musicians were playing that was influenced by R&B/gospel/etc., there aren't only simple songs, as can be heard in Preston's music and many other songs that had added arrangements. Even Little Richard.
This makes me think you are referring to only R&B and gospel (which white musicians named 'rock 'n' roll'). If this is the case, this type of music wasn't exactly popular in the way we think of popular music nowadays, not until white musicians 'appropriated' it.
As you can see, there is some incompatibility with what you're saying. 'Popular songs' did not only consist of rock 'n' roll songs, even though rock 'n' roll was considered popular music in the 50s. I mean, Jo Stafford made so-called traditional pop music, and they weren't exactly simple. If you read about late 70s British 'rock', you'd remember that 'rock 'n' roll' was a dirty word associated with the lower classes, drugs, and misfits, which was not necessarily part of popular music. Unless you mean popular music as opposed to 'classical music' (not the 'classical' from the period within 'classical music', mind you).
I don't want to get into a whole Beatles debate, but Beatles took from many styles and genres. So it isn't exactly fair to compare them to typical rock 'n' roll music, which they themselves started playing and were being trained to play initially.
Incidentally, the Beatles' influence is overstated--they usually popularized the innovations of others rather than innovating themselves. They were influential by virtue of their popularity, but they weren't as original. Pierro Scaruffi overstates his point perhaps, but has written the quintessential polemic against the myth of the Beatles: http://www.scaruffi.com/vol1/beatles.html
And 3), rock and roll didn't kill art music, or rise from its ashes. It's a separate thing all together, with its roots in earlier popular music genres. (jazz, bluegrass, the blues...) Rather there was significant cross-fertilization between rock and the not-quite-dead-yet art music sub-genre of minimalism.
The first C chord on a guitar is easy to hit with no finger twisting required. It's also easy to switch between the first C, Am, and G chord, you can even do it quickly and repeatedly while drunk as you can imagine many pop songs are written. The first F chord requires a little more careful finger placement but still easy to get too. Sure enough you hear this over and over in pop songs, some simple sequence of C F G A chords over and over.
Not surprising that the complex guitar chords that require six pencil-thin rubber fingers and a degree in music theory to know how to play aren't heard as often.
This is the reason why the guitar strings have the tuning they have, and not any of the million other possible combinations.
C major / A minor are even easier on piano. (C major and A minor are relative keys – they contains the same notes, just with a different note emphasized as the root, or tonic.) They're the two keys that are made up of just playing the white keys on the piano. In contrast, G major / E minor is probably the easiest key to play in on guitar (containing G, C, D, Em and Am), and it comes in second place.
Also, barre chords enable you to play in any key you want, so it's not like playing in C# is particularly harder than playing in C.
(1) People learn to play guitar by playing popular songs. These popular songs feature a subset of chords in certain combinations that sound good (eg. C->G->Am->F, C->Am-F-G, Am->F->C->G).
(2) People start creating their own songs using the mental maps of "what chords sound good together" from step #1.
(3) Rinse, repeat
My feeling is that it helps that these patterns are easier to play in C, but I think it's really about matching the "what chord comes next" pattern to a particular key.
The popularity of C and Em as keys is undoubtedly a result of what's easy to play on a standard guitar with no capo, but I see no correlation between chord popularity and ease of playing.
The modern 6-string guitar became popular in part because it was good for the kinds of music people wanted to play. I, IV, V, and vi (C, F, G, and Am) have a long history after all.
It's an interesting idea, that the evolution of music might be guided by an interplay between people choosing and designing new instruments to suit their tastes, and people developing new musical tastes using whatever existing instruments happen to be available.
At least your response tells me why this is the case. Thanks!
I wish he separated out the major keys from minor keys. It's easy to tell the difference; almost no-one writes pop music in the natural minor (which shares a key signature with the relative major), as it has no dominant fifth. Rather, melodic and harmonic minor keys are used, which have a distinct key signature from major keys (both have the 7th note of the scale raised to accommodate a dominant fifth chord). This should make them easy to detect.
The "Chord Use" chart also does not say much; C, F, and G are the I, IV, and V chords of the key of C major (the Roman numerals indicating their relative position in the scale), which together form the basic pop progression. Much more useful would have been to bin the chords relative to the key in which the song is written, rather than as their absolute pitch.
What I would also like to see is a histogram of chord progressions, e.g. I-IV-V vs. I-IV-ii-V vs. I-vi-VI-V etc. His preview of next week hints at this, but again he should use relative chord names rather than absolute chord names.
The preview graph, "Chords following em", is not very surprising either. Since this is an absolute chart rather than a relative one, we must assume that the data is reflective of the chord's use in the most common key (C). (Em will rarely occur in a song written in Am; rather, it will be altered to an E7 dominant chord.) Of the other chords available in the key of C, C and G both share two out of three notes with Em and thus are unlikely to be used due to lack of motion between them. Bdim is rarely used in C.
This leaves Dm, F, and Am as likely to occur following an Em. The E and B notes of the Em chord are a half-step below the next higher note in the scale, so they will tend toward upward motion, meaning the next chord will likely contain an F or a C. F contains both of these, hence its prominence in the graph. Both Am and Dm contain one of these notes; however Em->Am is an upward (downward) skip of a fourth (fifth), which is a resolving motion – it is likely that the next few chords following these two will be Dm, G, and C, to continue this motion. Em->Dm, being a skip of a second, does not share this property and hence should not be as common.
C and a-minor, F and d-minor, and G and e-minor are related chords, and can be interchanged in a standard progression for a different "feel". So it makes sense that e-minor would go to F (V to IV transition) or a-minor (V to I) more than any others. It's interesting that C and d-minor are under-represented in that transition.
It's interesting that the possible chords are all simple triads, with no options for extra tones. A C6 with particular notes in the bass could be interpreted as an a-minor, for example. There's a fair amount of ambiguity there.
The most popular chords are the good old I, IV, and V, and the next most popular are their relative minors (C -> am, G -> em, F -> dm).
The example they give of chords following "em" is also pretty much what you'd expect. The most classic resolution for "em" would be "am" (it's dominant -> tonic in the relative minor key).
The more popular resolution here ("em" to "F") is more of a pop music thing, because it's harder to do classical voice leading with it -- classical composers tended to avoid parallel fifths.
Edited to add: Why mention classical rules at all in a post about pop music? Because there's not much new under the sun -- you'd be hard pressed to find any harmony in pop music that Mozart or even Bach wouldn't recognize.
However, as you can see in the Hooktheory database, there are many progressions that seem to be unique to popular music.
You mentioned iii->IV, which is a no-no in classical music due to the parallel fifths (more common: V/vi -> IV). But also look at progressions like: C G Bb F, which is extremely common in pop. Here we have a double plagal cadence set up by the dominant that was never used by Bach or Mozart, which is probably best functionalized as: I V IV/IV IV
Atonality, on the other hand, is a more recent development in Western music and is defined as the lack of a tonal center. Atonality can be an extremely interesting way to write music. Some of the first atonal music (note how it's not markedly "dissonant") can be found in Debussy's Prélude à l'après-midi d'un faune[1] and the prelude to act I of Wagner's Tristan und Isolde [2].
I don't listen to a huge amount of pop music, but is there anyone out there that is at least experimenting with atonality?
[1]http://www.youtube.com/watch?v=9_7loz-HWUM [2]http://www.youtube.com/watch?v=1Bwl3GYBM3E
I don't buy that Eb/Cm is the third most common key in pop music, though. There's not a whole lot of pop music in minor keys, and Eb is a weird key to play guitar in.
Van Halen did it all the time. (Tuning down a 1/2 step is not uncommon among heavier rock/heavy metal bands. I'm not entirely sure why though.)
In my informal survey of the first 6 songs I got on the "pop" channel on pandora, fully a third were in minor keys. (Rumor has it by Adele, and I wanna go by Britney Spears)
The results are exactly as I would expect. F is the most common chord to follow E, because that's the primary way to resolve the dissonance of that note in C major. When E appears in other chords in C Major it will also tend to resolve to F unless there's a good reason not to (cadential 6-4).
A minor is the next most common after F, because that's the next step in a descending circle of 5ths pattern (E, A, D, G, C)
The only pop/rock use of II that I can think of is as a turn to drive II7 -> V7 -> I.
Coming up with a computerized vocabulary for the elements of coherent large-scale composition structures would be more of an interesting area to research than individual chord transitions, because the latter is really a solved problem.
MC trained on classical composers: http://www.youtube.com/watch?v=qOZ2Q-Ls48U
Iannis Xenakis was a major 20th century composer who incorporated MCs into some works: http://www.youtube.com/watch?v=DTzOWKaDrVI
Haven't seen a serious effort with pop/rock though. Lyrics might be the sticking point.
And if you fix this... well... you'd end up with chord progressions essentially indistinguishable from the sampled pop music. But that would be an awfully complex way to obtain results that you could just as easily do by hand. :) In fact many people can just vamp those chord progressions in real time if you don't expect too much creativity.
You can find the source code here : https://github.com/Feni/Infinite-Music-Machine
But like a lot of other people in here have been saying: There's more to a song than the chord progression. We might as well have been talking about rhythm - the vast majority of Western music is in 4/4 time. Also, practically ALL Western music uses the 12-note system. Not pointing this at you, but it's annoying to hear all the people in this thread complain about how pop music sucks because it's all based on the same foundation. Practically all computer programs are in some way based on C. Does this mean that all computer programs suck?
It's a well-known pattern; sorry the internet let you down.
The main problem in analyzing tonal music is that we mainly listen to relations between chords. For instance, in the following progression in C major, A major functions as a dominant of D (D is the dominant of G and G is the dominant of C):
C A D G C.
E A B E.
The number of repetitions also matters. Tonally, the progressions C | C | C | G | G and C | G | C | G are the same as C | G. Is he eliminating repetitions in the analysis?
About using A major in C; you can use it as a dominant of D (see my 1st example) or as a chromatic mediant [2] in C major. Of course, in modern music you can use anything you want, but these two are the most common uses.
And, naturally, the types of chords used will vary according to the music style.
[1] http://en.wikipedia.org/wiki/Tonicization [2] http://en.wikipedia.org/wiki/Chromatic_mediant
I hope that other articles on HN don't fall apart like this if you know a little about the subject.
That said, the whole attempt is impressive (from an engineer's perspective)
This may best thought of as a lexical analysis of 1300 popular novels. E.G. what is the most popular word following the word "it". The key of a tune 'controls' the chords available, using a typical chord progression. A song in the key of C most typically has the progression C-F-G or I-IV-V in roman numerals signifying 1 for the dominant C, and 4 and 5 for F and G respectively the fourth and fifth notes in the key's scale.
More interesting might be what are the most popular chord progressions. E.G. I-IV-V or II-IV-Im. Which is what I was expecting to click through to.
A million monkeys can write a hit in how many years, now? And BTW "it was a dark and stormy night" don't you know.
http://www.youtube.com/watch?v=I1DIgPyxiWU&feature=relat...
While I do believe the popular songs follow some pattern, I think the chord progression is only a subset. Someone should look into why Call me Maybe is so catchy. Seriously though
The "comfortable" bit is the easy part. Making it interesting is the trick. There are thousands of songs using this same progression that are awful.
That's my main objection to the original post, and similar articles I've seen. It doesn't really tell you anything usable about how to write a good song. At no point as a developing songwriter does looking at a statistical breakdown of chord progression help you take the next step. "It's got the same chords as X, so it'll definitely be good!" is not something you hear good songwriters say.
Edit: To clarify, I think I'm agreeing with the sentiment of your last 2 sentences, as I understand them.
http://www.youtube.com/watch?v=JdxkVQy7QLM - Rob Paravorian on how so many songs have the same chord sequence as Pachelbel's Canon in D
Also, the fact that he found D, E and A among the results is probably because of modulations. It's VERY common for pop songs to modulate a whole step during some chorus near the end [1]. As mentioned, G, F and C are V, IV and I. If we modulate a whole step, from C to D, the V, IV and I are A, G and D. It would be nice to consider those modulations into the research.
About the key choice, I believe it's irrelevant. It depends a lot on what's your instrument (Bb, Eb is easier on brass instruments), your style (lots of Metal songs in the key of E because E is the lowest note on guitar), your tuning (lots of rock bands downtune their guitars to Eb or D etc), your proficiency, and, most important, the vocalists range.
--
[1] Otis Reeding - My Girl, Celine Dion - Because You Loved Me (actually lots of songs by her), Monty Python/Eric Idle - Always Look On The Bride Side of Life, Talking Heads Nothing But Flowers (If you search "whole step key change" you'll get a bunch)
In other words, "C G a F" isn't materially that different from "G D e C" or "F C d Bb". All three are instances of the same progression: "I V vi IV" ...which happens to be the most hackneyed (or "effective", depending on your point of view) chord progression in popular music over the last 30 years.
If you transform each chord progression into its figured representation then you can pick up more significant trends such as the above, or blues changes (e.g. "I I I I / VI VI I I / V VI I I") and then you can start to discern when they rose to popularity and which ones are falling out of favor.
For example, in the 50s and 60s, I have no doubt "I vi IV V" was more popular than "I V vi IV" but I have no way to prove it currently and would love to find out if I'm right or wrong on that.
Hooktheory stores all of its chord progressions in relative notation so we have tools to answer questions like the one you've posted here. Although the Hooktheory database is relatively small, we have 20 songs that contain I vi IV V, compared with 100 songs containing I V vi IV. Just by visual inspection, of the songs that contain I V vi IV, none of them were written before 1975, which may not prove, but certainly supports your claim.
It's a great article, but I think he may have done a lot of work to find out something that is fairly common knowledge lol. Still cool though to have the supporting data. (edit: it would be cool to make this an interactive piece of data presentation to help you write songs. Also, the I, IV and V chords are so popular because they naturally make people feel good. It's why they show up so often in 'pop' music. minor chords have a more depressive quality to them)
Also, if you need proof that certain chords show up often in music, just listen to some Nickelback. Here is a fun link (that I THINK works. my speaker only works in the left side ;) ) http://dagobah.net/flash/nickelback.swf
This page contains the specific Chord Progression Maps for all twelve keys: http://mugglinworks.com/chordmaps/chartmaps.htm
We spent a lot of time doing this sort of stuff to flesh out harmonic and melodic patterns/meaning of pieces while at music school. To (grossly) simplify, it's essentially a form of reduction analysis, but the final step of the analysis is always I - V - I chord progression (tonic - dominant) with the 3 blind mice melody above (stepwise descending). I never found the final reduction particularly useful as, though he had a point about the prevalence of the tonic dominant relationship, it was over blown. The reduction steps were very useful for stripping away flourishes though, in order to see what was happening at a more base level in a piece (we analyzed a lot of Mahler this way).
Kinda like Map/Reduce in some ways.
Schenkerian analysis is a ton of fun, although you have to remember to just use it as a tool and not take it too seriously.
http://webcache.googleusercontent.com/search?q=cache%3Ahttp%...
Didn't Pandora radio did the same analysis for its recommendation engine?
I would say that this is most often limited to music that falls outside of pop culture, though. Katy Perry doesn't need to create movement or flow because emotional expression on the backing track is not what her music is about. The Raconteurs might, though. But once you get to that point you have to make the distinction between notes and chords.
[1] http://www.wired.com/listening_post/2008/04/a-scientific-at/
[2] http://www.wired.com/listening_post/2008/05/survey-produced/
1. Normalize for key: Express chords as I, ii, iii, IV, etc. This will permit analysis of chord progressions/exceptions (see below) across all keys.
2. Detect common constructs, e.g., 8-12-16 bar Blues, and analyze for exceptions, e.g., use of vi instead of I, use of V versus V7 as turnaround, etc. (And more interesting exceptions, e.g., resolution to ii or iii instead of I, etc.)
3. Related to #2, search for popular songs that do NOT follow/use common constructs. Are there are common characteristics across "second rank" popular songs (by which I mean "popular but not quite smashes, or short-duration - novelty - smashes")?
4. How much variation in key and/or chord progression is there for each artist?
Comments:
A. Not much of a surprise that C/Am is the most popular key: It is the most accessible - the white keys of the piano. It is also very accessible on the guitar, once one learns F...
B. ...but surprising to me that E is so unpopular, being "the natural key" of the guitar (E, A, B/B7 being so easy to learn and so common to the Blues). Analysis of key use by decade - or genre - could prove interesting....
C. Keys these days (the days of equal temperament) are chosen largely on accessibility: Can the soloist hit all of the notes important to the key? Can the accompanist make all the chords important to the song? Once upon a time, prior to equal temperament, keys had sounds and feels of their own, but nowadays, with equal temperament, the progression from unison to octave is by steps of absolutely the same value in each key.
By pure combinations it seems the space of melodies is very large. But this space is in fact dramatically shrinked by the very strict relationships imposed on subsequent tones and the result could be that "we have finished exploring the space of interesting melodies", we are deemed to repeat ourselves, musical invention is something of the past.
Regardless, I will be keeping tabs on this. Hah, totally didn't intend that pun.
Ask any singer: F is the hardest key to sing in. Most people who have to sing in F unaccompanied will inevitably go flat over the course of the song without lots of practice.
I would have plotted the frequency of each chord relative to the key. (e.g., count chords as I/IV/V/ii/etc. instead of C/F/G/Dm) This automatically corrects for the relative popularity of different keys seen earlier in the post.
It actually makes we want to try writing some things avoiding the most common progressions to see what comes out.
With regards to other genres and other time periods, I think you'd find pretty similar data with what was "popular" at any given time. Although there have been composers who push the limits, and with some success, our brains seem to be hard wired to react well to the mathematical correlations that are present in the chord parings. On the other hand, perhaps the more exposed we become to varied chord progressions, the more pleasing they would sound.
There is a very interesting RadioLab episode exploring the rage that incited at the premiere of Stravinsky's "The Rite Of Spring". Essentially, scientists are learning how the brain reacts to dissonance in music. The story begins about 32 minutes in.
http://en.wikipedia.org/wiki/The_Axis_of_Awesome#Four_Chords...
They've said that the chords are used by some of the most well known songs in the world, and their performance demonstrates this nicely, as in this clip:
http://www.youtube.com/watch?v=oOlDewpCfZQ
The above link is the official video; but they explain their reasoning better in this live performance:
Oh, and a G chord isn't any easier to play on a guitar than a C# chord.
The point of music, or any art, is to evoke an emotive response from the audience. To equate the "quality" of art to the technical abilities of its creator is essentially to reduce it to something more akin to juggling knives or spinning plates. Art isn't about virtuosity, it's about emotion.
But hey, if that's your thing, there are a ton of Dream Theater records available on iTunes.
(ya, I consider Radiohead "pop music")
Melodies are mildly interesting. It's harmonics that are an endless source of mystery.
In the world of rap music, the sonic innovation has been extreme. The meaning of a Public Enemey "song" cannot be assessed through this type of analysis.
My sense, as a classical and electric (contemporary rock / blues) guitarist is that you'd observe interesting deviations from the aggregate results described in the study.
Digging a bit I found the following research piece which shares some more thoughts on this topic:
I know Pandora has done some analysis like this for their database, but I thought it was limited to things like major or minor tonality, upbeat tempo, etc. and didn't delve as much into the nitty gritty harmony. One reason for this might be that these patterns are so universal (spanning lots of genres), that it might not be too helpful for determining what types of music people like. I could be wrong about this though.
Pop music is all about the simple melody, in terms of impacting a recognizable pattern on the brain. That is why it's popular, and you see the same melodies repeated over and over, and over, and over.
Edit: signup gave me an error 500, though.