Harper will make an appearance tonight on Michael J. Fox’s ABC special “Adventures of an Incurable Optimist.”

The musician and Fox will do a little jamming together and then discuss the effect of music on mood.

Other celebs making an appearance on the show include Lance Armstrong, Bonnie Hunt, Bill Murray and Tracy Pollan.

In case you miss the show or your DVR is on the blink, the special will be available at ABC.com beginning tomorrow morning.

Thursday, May 7
Jen Kirkman, Randy Sklar, Jason Sklar – “Chelsea Lately”
Faryl Smith – “The Bonnie Hunt Show”
Norm MacDonald, Animal Collective – “Late Show with David Letterman”
Ben Harper & Relentless7 – “Late Night with Jimmy Fallon”
Flo Rida – “Jimmy Kimmel Live!”
Black Kids – “Last Call with Carson Daly”

Friday, May 8
Whitney Cummings, Kevin Hart – “Chelsea Lately” – rerun
Diana Krall, Lewis Black – “The Hour with George Stroumboulopoulos”
Brian Regan, Chris Cornell – “Late Show with David Letterman”
Jewel – “The Tonight Show with Jay Leno”
Joan Rivers – “Late Night with Jimmy Fallon”
Scott Weiland – “Jimmy Kimmel Live!”
Ida Maria – “Last Call with Carson Daly”

Saturday, May 9
Lyle Lovett, John Hiatt, Guy Clark, Joe Ely – “Austin City Limits” – rerun
Justin Timberlake, Ciara – “Saturday Night Live”