LONDON (AP) — A British research team has identified three major trends in popular music with the emergence of hip-hop judged the most significant.

The researchers analyzed roughly 17,000 songs that were in the U.S. pop charts between 1960 and 2010.

They identified three major revolutions: the "British invasion" in 1964; the 1983 "new wave" movement based on synth-based songs and the 1991 arrival of rap and hip-hop on mainstream charts.

The analysis of instruments used, chord patterns, tonal character and other factors found that the mid-1980s was the period when pop music was least dynamic.

Researcher Matthias Mauch says the Beatles, Rolling Stones and other British bands followed existing trends while the impact of hip-hop was deeper.

The study, released on Wednesday, was conducted by the University of London and Imperial College.