In a once-in-a-lifetime experience, KPFA presents the four-hour fund-drive special: Bob Dylan at 80. KPFA programmers Derk Richardson (“The Hear and Now”) and Larry Kelp (“Sing Out”) co-host this birthday salute to Bob on Wednesday, May 26, from 8 p.m. to midnight. As they have done for 30 years, Derk and Larry present a mix of the Nobel Laureate’s greatest songs, original recordings, explosive live performances, rarities and incisive interpretations by fellow artists ranging from Mavis Staples to the Grateful Dead. Far from retiring, Dylan received unanimously rave reviews for his most recent album “Rough and Rowdy Ways,” considered among the best of his 60-year recording career.