At least once a year, producer Frank Peterson retreats with his headphones to raid his extensive music collection in the search for new repertoire. It takes a lot of instinct and inspiration to choose the songs for a project like Gregorian. "Not every song is suited for the Gregorian sound scale," he explains, "so the songs have to be chosen very carefully for Gregorian." Luckily, Peterson's immense music knowledge seems inexhaustible and there are no limits to his creativity. How else could it be that we find a Eurythmics ballad next to a Tears For Fears pop tune in the Gregorian repertoire? Or a Peter Gabriel song next to a Lenny Kravitz rock track? However, with Gregorian all of this fits in and forms a unit - well-known melodies in a completely new sound transporting the listener into the timeless world of Gregorian chant.