The singer, Samuel Schultz, said in an interview in August that the two men assaulted him in May 2010, when, as a graduate student at Rice University in Houston, he had gone to hear Mr. Daniels in Handel’s “Xerxes” at Houston Grand Opera. After attending the performance and cast party, Mr. Schultz said, he was invited to Mr. Daniels and Mr. Walters’s apartment. There, he said, he was given a drink that caused him to lose consciousness. He awoke alone, he said, naked and bleeding from his rectum.

A lawyer for Mr. Daniels and Mr. Walters denied the accusations. “David and Scott are innocent of any wrongdoing,” their lawyer, Matt Hennessy, said in a statement. “Sam Schultz is not a victim. He never would have gotten this much attention from his singing, and he knows and resents that fact. He waited eight years to complain about adult, consensual sex to ride the #MeToo movement to unearned celebrity. We will fight this.”

Mr. Schultz said in an email that he had been told about the arrests by the Houston police, but he declined further comment.

Mr. Schultz said over the summer that he had initially been afraid that making the accusations would damage his fledgling career. But he went public last summer — first anonymously, in an online post, and then naming Mr. Daniels and Mr. Walters as his attackers in an interview with The New York Daily News.

A Houston police officer, D.H. Escobar, wrote in the charging documents that he had found Mr. Schultz, who was identified in the report only by his initials, to be “credible and reliable.” The officer said that he had met with a therapist Mr. Schultz consulted in 2010, and that her notes were consistent with what Mr. Schultz had told the police. The officer said that he had also reviewed medical records which showed that Mr. Schultz had sought medical attention “as a result of the sexual assault” on June 1, 2010.