Groton police said officers responded to Geils home around 4 p.m. Tuesday for a well-being check and found him unresponsive. He was pronounced dead at the scene.
"A preliminary investigation indicates that Geils died of natural causes," police said in a statement.
The J. Geils Band was founded in 1967 in Worcester, Massachusetts, while Geils, whose full name was John Warren Geils Jr., was studying at Worcester Polytechnic Institute. The band, whose music bridged the gap between disco and new wave, released 11 studio albums before breaking up in 1985. They reunited off and on over the years.
The band had several Top 40 singles in the early 1970s, including a cover song "Lookin' for a Love" by the family group The Valentinos and "Give It to me."
Their biggest hits included "Must of Got Lost," which reached No. 12 on Billboard's Top 100 in 1975 and "Love Stinks," a rant against unrequited love, the title song on their 1980 album. Their song "Centerfold," from the album "Freeze Frame" was released in 1981 and eventually charted at No. 1 on the U.S. Billboard Hot 100 in February 1982. It stayed there for six weeks and was featured on MTV.
When news of Geils' death broke, fans turned to social media to offer condolences and to reminisce about the band's songs and concerts.