"A study of music from the '50 to the present
using the Million Song Dataset has concluded that modern music has less
variation than older music and songs today are, on average, 9dB louder
than 50 years ago. Almost all music uses just 10 chords, but the way
these are used together has changed, leading to fewer types of transitions being used. Variation in timbre has also reduced over the past decades." via Slashdot