How often does the man visit his grandparents

At fourteen, he once heard a famous song in Rome (罗马). Mozart heard it (26) once and (27) home. There he (28) all by himself. Every note of it was quite good. (29) could believe that this could be done, so he was put alone in a room with people at the door and he did it again. Stories of his good (30) spread all over Italy.