Complex sentence: Simon asked the band permission to include a cover version of the song in an album, to which the band replied that the piece belonged to Andean folklore, while the arrangement was Jorge Milchberg's (director of Los Incas).
Split into simpler sentences: Simon asked the band permission to include a cover version of the song on an album. The band advised him that the piece belonged to Andean folklore, while the arrangement was Jorge Milchberg's (director of Los Incas).