Even though patient Garrett Lambert is in an “isolation” room at Memorial Sloan Kettering Cancer Center in New York City, meaning visitors must don masks and gowns to enter, music therapist Holly Mentzer’s harp makes the enclosed room feel like a serene, welcoming space as she and Lambert harmonize. Lambert says “Don’t Let Us Get Sick,” written by Warren Zevon, is one of his favorite melodies to sing and strum in the hospital. “Don’t let…