They sing a song of joy—and of good old-fashioned rocksteady reggae. The Melodians, Jamaican-bred legends, are still performing over 40 years after forming, bringing their quintessential Rastafarian sound all over the world. Best known for the feel-good anthem “Rivers of Babylon” from The Harder They Come (“Carry us away captivity / Require from us a song”), the Melodians are exuberant, sincere and sentimental. Since founding member Brent Dowe suffered a heart attack in 2006, original members Tony Brevett and Trevor McNaughton have soldiered on. Groove with them on Friday, July 1, at the Mystic Theatre. 23 Petaluma Blvd, Petaluma. 8:30pm. $21–$23. 707.765.2121.