Simplify the following text for a Grade 9 native English-speaking person.
Original: The best known musical depictions of mermaids are those by Felix Mendelssohn in his Fair Melusina overture and the three `` Rhine daughters '' in Richard Wagner 's Der Ring des Nibelungen .
Simplified: The best known musical about mermaids are those by Felix Mendelssohn in his Fair Melusina and the three `` Rhine daughters '' in Richard Wagner 's Der Ring des Nibelungen .