OTOH, I was quite surprised that E minor is used more (17%) than E major (10%) in popular music. In classical music the latter is quite common and the former is very rare.

On a guitar in standard tuning (EADGBE), the Em chord can be played by fretting only two strings (the A and D), both on the 2nd fret. It's basically the easiest chord to learn to play. And if you start in Em, it pairs with G, Am, C and D -- all of which are also very simple fingerings. Correlation isn't causation, but I'd bet dollars to doughnuts this is a factor, given the absolute dominance of the guitar in popular music songwriting.

It's not about E major as such -- all the songs were transposed to C major/A minor scales. It's about chord III in major scale or chord V in minor scale. In classical music chord III is basically never used in compositions in major keys. In minor key music, chord V is typically altered to major as it leads to the tonic much better. Often, for instance, melody ends in G# and A. Minor V, on the other hand, is kind of ambiguous and rarely, if ever, used.

EDIT: Thinking about it, E minor is fairly common in phrygian scale (it's the tonic chord), however, phrygian, unlike dorian or myxolidian, which are used at least sometimes, is super rare -- its dominant chord, B dim, is dissonant, which kind of sucks.

Phrygian is quite common in metal, along with phrygian dominant. Great scales for dissonance and tension.

Functional harmony kind of goes out the window once you stray from the major/minor modes anyway. You have to lean heavily on the root to maintain the tonality, or else the perceived key center tends to shift.

Ah, I haven't been aware of usage of phrygian mode in metal music. Maybe that's what skews the ratio of Emaj/Emin towards the latter?

The author notes that the analysis is based on 1300 songs from the Billboard top 100 in the last 2 years.

I think it's safe to say the effect of metal songs using phrygian is negligible.

And the phrygian used in metal has modified major third (G# instead of G) which, again, results in E major, not E minor chord.

The minor V is used a lot in reggae and modally based music

This is written with all songs converted to the key of C though. So in guitar-friendly keys you're probably looking at the key of E and there the Em becomes G#m; or key of A and C#m.

Sure -- slap a capo on the 4th fret and there it is. :)

(Also, songs are often written in one key, then transposed in the studio.)

Oh, I wouldn't slap it on the fret ;)

There’s a key frequency chart and it makes sense that C and G are so popular. What didn’t make sense to me is why D and A aren’t more popular. Eb and F are somehow more popular. If this list is dominated by guitar, I’d expect D and A to be more popular since you can play I, IV, and V in those keys using open chords.

Eb is probably disproportionately popular due to the common practice of tuning guitars down a half step, making Eb instead of E the natural/easy root chord.

I'm not sure why F would be more popular than D and A. One hypothesis would be that it has fewer accidentals; it's not a fun key for guitars, but many contemporary pop songs aren't guitar-driven anyway.

Hypothesis time: the predisposition to flats is due to Big Band, Blues and Jazz music being predisposed to it. And there it is logical due to the B flat and E flat tuning of the horns (their C is our B flat or E flat).

Make life even easier with an Em7!

Em7 is easier to argue for. It's basically the dominant (G mojor) with added 6th.

They transposed all songs in C in order to be able to compare chords by name (which is a weird methodology but whatever).

By that measure it's only natural that Em (iii) is more common than E (which is non-diatonic to C).

With GFC being most popular, I'd expect Em more, because it more fits with those major ones.

Emin vs Emaj - my gut would say Emin is going to fit in with keyboard/piano stuff easier, and there's more of that type music overall. When I think Emaj, I think guitar stuff (EAD stuff), and there's been less of that overall compared with keyboard-based music.

Em is the iii chord in C, and it’s rarely used because it doesn’t really add any movement. Harmony is all about the cycle between tension and release, and there are other chords that do a much better job at filling the roles a iii chord could have.

It’s useful for dreamy and somewhat static chord progressions though.

True. Was thinking more about the G - again, another common pianoish base (in my experience, anyway).

D/E/A - again, ime - were always "guitarish" songs. GCF always seemed to be more "pianoish". Just my own observation/experience - it may not be true of everything, but seems to be true about much of the stuff I've listened to (and tried to play).

Yeah, C major (C/F/G) can be a bit awkward on guitar, the F barre chord is a painful hurdle for new players to get over.

A major (A/D/E) is probably the easiest key to play. G major is arguably the most useful, because you have access to all the important chords in open position: G, Am, C, D, Em.

If the most popular key is Cmaj, Emin makes more sense than seeing Emaj.

Technically C major is not a key, is a chord.

It’s both.

Ok I checked the terminology and you're right, in Italian we call it "C natural" to distinguish it from the chord. Apparently in English you don't.

Context makes it clear whether the topic of discussion is the key of the song or a type of chord.

Also, in this way we can say "C major" or "C minor" to refer to the key of the song. We use "natural" when its important to distinguish from a note that has a sharp or flat - e.g. C# versus C natural.

In Italian, how would you refer to the key of Db major - "Db natural"? How would you refer to the key of Db minor?

You just specify the "minor", "major" is implied otherwise.

The Em is the "default" guitar chord --sort of like the C scale is the "default" piano scale (easiest, most convenient, etc)...

Not that surprising considering natural C is the most common key for songs.