Police say Dr. Ilya Lehman, 70, touched the third-grader on numerous occasions and forced her to touch him at least five times over the course of several months to two years.
It is alleged to have occurred during the school year and stopped during the summer months, only after the girl's mother walked in on them during a lesson in her home.
Lehman, who heads the Early Ear music school, was arrested at Kennedy Airport on July 15 as he was returning from Russia.
He was initially in court on Wednesday, but the appearance was postponed until Thursday after he requested a Russian interpreter.
Police are asking that any parents of children who have worked with Dr. Lehman directly contact the District Attorney's Office Child Abuse Hotline at 212-335-4308.
If parents plan on speaking with their own children about this matter, it is recommended they consult the DA's Office or an appropriate website for guidance on such conversations.
Lehman is charged two counts of sexual abuse and was held without bail.