I'm not sure if it was the dynamics specifically, but it was clear to me that A was human. Within 30 seconds I was so sure, I hit pause and loaded the answer to see if I was right (I was, and I'm likely the worst pianist on these forums and only a casual fan of music that falls into the 'classical' genre.)
Here's[0] a fabulous physics paper that analyses the 16th notes by a studio drummer widely considered one of the best in his field. IIRC, the paper mentions he couldn't record with a click because it'd throw him off. That being said, the quality of the recording didn't suffer (his 2nd take of the track was more than good enough for the rest of the musicians to record against). So his own 'internal metronome' was more than good enough. The interesting thing wasn't that his syncopation was incompatible with a click track, but rather the skew which evolved throughout each phrase had a mathematical model that fit well against it. The study compared his recording against a corpus of user submissions of the same track and all of these drummers universally followed a similar set of dynamics. So presumably all humans (or at least, all western drummers who elected to submit their recordings) have that same skew intrinsically.
It's interesting whether it's a byproduct of culture (like an accent) or a feature intrinsic to humans. In fact, that itself would be an interesting study -- compare the patterns of a traditionally schooled western jazz drummer vs a tribal African drummer with vs an Indian tabla drummer. The end of the paper suggests additional avenues to explore, but who knows, maybe soon drumming will be 'solved' ?
I'm totally with you on seeing how it would do training against a specific set of recordings from a specific region and/or era. The results would be terribly interesting ! Or training just against some particular virtuoso like Gould on Bach or Horwitz on Chopin.
As I understand it, there are basically just a handful of songwriters out there (Shane McMcAnally is a prime example) who write songs for the major country-pop artists. If you have a listen to this[1], you can really see how similar each song is. (This isn't exclusive to country music - the 90s pop I grew up loving is pretty much the same, as demonstrated by Rob Paravorian[2].) There's probably a lot of money in automated songwriting for Katy Perry & her entourage. Startup idea for any of you kids.
IIRC, there's a startup which is already using pinterest, tumblr, and more obscure sites like lookbook to analyze and generate trends for clothing and interior design which design houses can pay semi-nominal fee to gain access to. H&M is great pumping out high-street fashion copies within a season, but imagine being able to actually beat Tom Ford to market.
There are also interesting sociological implications for this. The Culture of Chess changed with BlueGene. When I first read about AlphaGo I was floored. (I mean really. I had previously thought would be intractable within my lifetime due to the huge configuration space.) As we see these 'good enough' models emerge, this has wide implications on human culture as a whole.
I wonder how it will affect the value of artists (in any genre). An ex of mine who hated basketball (this was during the Kobe/Paul Pierce days) still managed to recognize the genius when I showed her some Michael Jordan clips. Certainly an artist in his craft. I'm not a fan of Lady Gaga[3] but when I saw this performance I could immediately see a significant amount of talent. Walter Murch is an absolutely amazing film editor, will he be reduced to a Final Cut Pro plugin? If I manage to get my hands on the all-22 recordings (for every NFL game, there's an overhead camera which records the whole field to let coaches analyze their opponents) of every American football team, can I out-tactic Bill Belichick ?
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[0] journals.plos.org/plosone/article?id=10.1371/journal.pone.0127902 (Seriously, it's a fantastic paper.) [1] https://www.youtube.com/watch?v=FY8SwIvxj8o [2] https://www.youtube.com/watch?v=JdxkVQy7QLM [3] https://www.youtube.com/watch?v=oP8SrlbpJ5A