Howard Fast, novelist who led the defense of the first Peekskill concert, will be master of ceremonies at the Shoulder-to-Shoulder Concert next Tuesday, March 28, at Manhattan Center. Paul Robeson is the featured performer. Proceeds will finance the two-million-dollar suit by the victims of Peekskill. Tickets are still available in Room 1613, 205 E. 42 St., Mu 4-6640.