Amazon Music Unlimited is Amazon’s music streaming service, featuring more than 90 million songs in high-definition audio which you can listen to on-demand and ad-free.

Ruth E. Rosenberg, a music professor at University of Illinois-Chicago, started studying 432-hertz music in the mid-2010s when a student mentioned a fondness for it.

Amazon’s new on-demand, streaming music service, Amazon Music Unlimited, has taken its first steps abroad after launching last month in the U.S. to go head to head with Apple Music, Spotify ...