Simplify the following text for a Grade 9 native English-speaking person.
Original: In 2003 , Thile teamed up with mandolinist Mike Marshall for the duet album Into the Cauldron , which included original pieces as well as pieces by Charlie Parker and J. S. Bach .
Simplified: In 2003 , Thile and mandolinist Mike Marshall made a duet album called Into the Cauldron , which had covers by artists from Charlie Parker to Bach .