As the Metropolitan Opera reeled from the suspension of its longtime conductor James Levine over sexual misconduct accusations, a fourth man came forward Monday saying that Mr. Levine had sexually abused him decades ago, when the man was a student.

Met officials scrambled to deal with the cascade of accusations, emailing donors to assure them that the Met will be taking “all appropriate actions” — even as the opera house came under sharp criticism for not investigating Mr. Levine after learning in 2016 of a police inquiry into a report of sexual abuse against him.

The Ravinia Festival also announced Monday night that it had “severed all ties” with Mr. Levine, its former music director, who had planned to begin a five-year term as conductor laureate in the summer of 2018. “We are deeply troubled and saddened by the allegations and sympathize with everyone who has been hurt,” the festival said in a statement.

The man who made the new accusations Monday, Albin Ifsich, said he had been abused by Mr. Levine beginning in 1968, when Mr. Ifsich was 20 and attending the Meadow Brook School of Music, a summer program in Michigan where Mr. Levine was a rising star on the faculty. He said that the abuse continued for several years after he joined a tight-knit clique of young musicians who followed Mr. Levine in Cleveland and later New York.