Complex sentence: In January 1999, the band began writing a new album, which was to once again be supervised by manager Bud Prager, who was credited with co-writing five of the album's twelve songs.
Split into simpler sentences: In January 1999, the band began writing a new album. The new album was again supervised by manager Bud Prager, who was credited with co-writing five of the album's twelve songs.