Afro Celt Sound System, as the name implies, fuses Irish and West African music with electronic dance music. I brought back one of my old favorites from their 1999 album Volume 2 Release (Real World Gold) this week. I used it in an interval class and included a seated fast flat road and a standing flat road. At around 67 rpm's, you could certainly use it as a hill as well. I've also included this one in my St. Patrick's Day playlists in the past, because it has a celtic feel to it for sure. If you're looking for a unique, instrumental sound, definitely check this one out.