Jon Fishman, Tommy Lee, O.A.R., will.i.am and Jordin Sparks are among the latest additions to the third annual Green Apple Festival. As previously reported, the multi-city Earth Day event will present an eclectic mix of free performances in Washington DC, New York City, Miami, Denver, Dallas, Chicago, San Francisco and Los Angeles on Sunday, April 20th.

In San Francisco’s Golden Gate Park, Fishman and Lee will both join Hart and a troupe of leading African, Cuban and Brazilian drummers for a performance that is being billed as Mickey Hart’s Mass Drum. The performance marks the first time Fishman and Hart have collaborated together onstage. The afternoon of music will also feature performances by Dan Hicks and The Hot Licks featuring Michael Kang, Yonder Mountain String Band and Brett Dennen. In addition, Fishman will play a Green Apple club show with Yonder at San Francisco’s The Warfield on April 18. Meanwhile in Los Angeles, Escalera (featuring pro-skateboard legends Danny Way and Bob Burnquist) has been added to Green Apple’ Santa Monica Pier festivities.

On the other side of the country, several artists have been added to Green Apple’s flagship event in Washington, DC’s National Mall. 19 Recordings/Jive Recording artist Jordin Sparks will now perform the National Anthem, while O.A.R. will kick off the day’s festivities at noon with a rare acoustic set. After performances by the DCC Boys Choir, Umphrey’s McGee, Warren Haynes, Thievery Corporation, Toots and the Maytals and Gov’t Mule, The Roots will close out the event with special guests will.i.am, Ne-Yo, Doug E. Fresh, Talib Kweli and Chrisette Michele. The Bacon Brothers have also been added to Green Apple’s New York Central Park festivities.