Jason Isbell and the 400 Unit closed their Thursday night (Aug. 26) concert with a tribute to late Rolling Stones drummer Charlie Watts, who died on Tuesday (Aug. 24). Opening act Brittney Spencer joined the band for a high-energy cover of the rock band's classic "Gimme Shelter."

With Spencer playing the Merry Clayton to Isbell's Mick Jagger, the band delivered a straightforward take on the song, written by Jagger and bandmate Keith Richards and originally released in 1969. "Gimme Shelter" opens the Stones' Let It Bleed album and is considered among not only their greatest.

Spencer, in particular, mimics Clayton's instantly recognizable vocals — a hallmark of the song with ease. Watch the full performance below:

Isbell and company were in Grand Rapids, Mich., on Thursday night. Spencer is joining them at select shows throughout the summer and fall, including one of the band's eight nights at Nashville's Ryman Auditorium in October; on Wednesday night (Aug. 25), she made her debut at the Ryman, as part of the 2021 ACM Honors, and brought the house down with a cover of Martina McBride's "Independence Day."

Fans attending all of Isbell's upcoming performances will be required to show proof that they have received the COVID-19 vaccine or tested negative for the virus ahead of the concert. He was among the first artists to institute such a requirement, and has moved shows and dropped out of festivals at venues that won't agree to the policy.

"You know, I'm all for freedom, but I think, if you're dead, you don't have any freedoms at all. So it's probably important to stay alive before you start questioning your liberty," Isbell says of those pushing back on the requirement. "It's life, and then it's liberty, and then it's the pursuit of happiness. Those are in order of priority."

Watts was 80 when he died on Tuesday. His cause of death has not yet been revealed, but earlier in August, the Stones announced he'd sit out their 2021 tour due to an undisclosed surgery. He'd played on every Rolling Stones album, single and tour for nearly 50 years, from 1963 to 2021.

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May they rest in peace ...

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