The outdoor, rain-or-shine concert will be held on the Great Lawn of the Vanderbilt Mansion, overlooking Northport Bay and the Long Island Sound. On the playbill: Wonderous Stories, Milagro, Half Step and Jellyband, recreating the music of The Who, Santana, Grateful Dead, Jimi Hendrix, Credence Clearwater Revival, The Band, Janis Joplin and others.  RAIN OR SHINE, NO REFUNDS