The city of Sarasota, Fla., has a project called “Sarasota Keys,” which installs lovely old upright pianos in public places where anyone can play. One day last week, a homeless man sat down at one of these sidewalk pianos at a public art exhibit and started playing the Styx’s “Come Sail Away.” Passersby took notice, pulling out smartphones to capture the moment and dollar bills to thank the musician.

Donald Gould, 51, a scrawny man of “cave man” appearance with scraggly hair and unkempt beard, kept his eyes on the keys and his music filled Main Street in downtown Sarasota, Fla.

Gould, or “Boone” as he is known around town, said he only wanted to earn a few bucks. A week later, video of his impromptu performance has been viewed more than 7.5 million times on YouTube and more than 5 million times on Facebook, with the videographer, Aroar Natasha,