BladeVenom
Lifer
What has changed is how the chords are spliced into melodies. In the 1950s many of the less common chords would chime close to one another in the melodic progression. More recently, they have tended to be separated by the more pedestrian chords, leading to a loss of some of the more unusual transitions. Timbre, lent by instrument types and recording techniques, similarly shows signs of narrowing, after peaking in the mid-60s, a phenomenon Dr Serrà attributes to experimentation with electric-guitar sounds by Jimi Hendrix and the like.
What music lost in variety, it has gained in volume. Songs today are on average 9 decibels louder than half a century ago, confirming what industry types have long suspected: that record labels engage in a "loudness race" in order to catch radio listeners attention.
Music has gotten stupider and louder.
http://www.economist.com/blogs/babbage/2012/07/science-music
http://www.nature.com/srep/2012/120726/srep00521/full/srep00521.html