Dr. Eric Walker, Anthony’s younger brother, tells TMZ ... the singer and musician passed away at an Ohio hospital last Monday -- this after he experienced complications from a neck surgery he was undergoing.

Unclear what exactly the procedure was meant to correct, or what went wrong -- but we're told Anthony died as a result. His sibling tells us the artist's life will be celebrated in his hometown of Chicago later this week.

Anthony's family tells us they thank his fans for their love and support during this tragic time.

Anthony joined the famed R&B/Funk band in 1979 ... contributing to the group as a dancer, choreographer and songwriter. Despite his late addition to the group -- which formed in 1967 -- Anthony went on to perform with GAP Band for the next 23 years as a core member.

The Gap Band notably appeared on "Dick Clark's American Bandstand," "Don Cornelius' Soul Train" and "Solid Gold." Anthony even did some moonwalking for Dick himself back in the day ... and he showed him how to do the cool move that Michael Jackson has popularized at the time.

In 1985, Anthony had a major music win thanks to a collaboration with Charlie Wilson -- the GAP Band's lead singer -- and bandmate Billy Young ... as they produced together the album "Billy & Baby Gap." Not only was it the first album released as part of a band member collab, but their single "Rock the Nation" hit No. 3 on the charts.

During his lengthy career, Anthony also collaborated with music legends Rick James and George Clinton. You'll even hear Anthony's percussion skills on Snoop Dogg's single "Snoop's Upside Ya Head."

Anthony didn't just make a splash with GAP Band ... he famously formed a break-dancing group, known as "Tidal Wave," in the '70s. They once even beat out the famed New York City Breakers in competition  ... in addition to nabbing several other awards during their run.

There's no doubt dance played a huge role in Anthony's career ... he taught at John Travolta's dance studio in the early '80s and even went on to work as a choreographer for Disney.

Prior to his passing, Anthony was spending his time performing with GapX ... a group formed by other former members of the Gap Band. He was 60.