The Million Song Dataset is an NSF funded project. The following density plots by decade were recently posted on Reddit here
https://i.imgur.com/KsFxc5Z.png
What kind of songs is this about?
“The Million Song Dataset is also a cluster of complementary datasets contributed by the community:
SecondHandSongs dataset -> cover songs
musiXmatch dataset -> lyrics
Last.fm dataset -> song-level tags and similarity
Taste Profile subset -> user data
thisismyjam-to-MSD mapping -> more user data
tagtraum genre annotations -> genre labels
Top MAGD dataset -> more genre labels”
The web page has active links to each of these datasets. My guess is that they are more popular song than Opera or lieder.
Edit: “The core of the dataset is the feature analysis and metadata for one million songs, provided by The Echo Nest”