The fourth Central Park Music festival, presented by the F. and M. Schaefer Brewing Company, will Open June 26 with Benny Goodman and Lionel Hampton. Mr. Goodman will have a 17-piece orchestra, his largest group in recent years.

Ron Delsener, festival producer, will present 33 concerts this summer. There will be two performances each evening; admission is $1 and $1.50.

Among those who will appear are Tiny Tim, Flip Wilson, Tom Paxton, Procol Harum, Thelonious Monk, Blood Sweat and Tears, the Grateful Dead, Joni Mitchell, Tim Hardin, Buffy Sainte-Marie, Mongo Santamaria, Sly and the Family Stone, Dizzy Gillespie, Buddy Rich, the Mothers of Invention and Nina Simone.