Simplify the following text for a Grade 9 native English-speaking person.
Original: In February 1684 he became Maestro di Cappella to the viceroy of Naples , perhaps through the influence of his sister , an opera singer , who might have been the mistress of an influential Neapolitan noble .
Simplified: In February 1684 he became Maestro di Cappella to the viceroy of Naples .