Simplify the following text for a Grade 10 native English-speaking person.
Original: The theme music , composed by Joseph LoDuca , who also co-wrote the lyrics for the songs in `` The Bitter Suite '' , was developed from the traditional Bulgarian folk song `` Kaval Sviri '' , and was sung by Le Mystere des Voix Bulgares .
Simplified: Composer Joseph LoDuca wrote the theme music and incidental music , and co-wrote the lyrics for the songs in `` The Bitter Suite '' . The theme music was developed from the traditional Bulgarian folk song `` Kaval sviri '' , sung by the Bulgarian State Television Female Vocal Choir .