Can't tell the difference between Greyson Chance and Katy Perry? A paper published in Scientific Reports might help explain why.

According to researchers from the Spanish National Research Council, not only has pop music become increasingly homogenized over the last 50 years, as well as "intrinsically louder." Reuters reports:
"We found evidence of a progressive homogenization of the musical discourse," team leader Joan Serra, an artificial intelligence specialist, told Reuters. "In particular, we obtained numerical indicators that the diversity of transitions between note combinations - roughly speaking chords plus melodies - has consistently diminished in the last 50 years."
For the study, the researchers decided to utilize the Million Song Dataset, which is "a freely-available collection of audio features and metadata for a million contemporary popular music tracks."

They determined that not only do all modern pop songs sound the same, but they've also gotten much louder. This so-called "Loudness War," is defined as "a terminology that is used to describe the apparent competition to release recordings with increasing loudness, perhaps with the aim of catching potential customers' attention in a music broadcast."

So basically, the pop genre is just blasting you with similar sounding songs in hopes that you'll be too confused to know the difference.