Employing the same skills he had applied to records by Smokie and Gilder, Chapman produced a more polished guitar and keyboard sound than the band had ever achieved, topped with layered vocals. The focal point of the album and the breakthrough single, was "Heart of Glass". The source of its driving disco beat is a matter of contention: Chapman claimed he had created the sound after the band had presented it as a slower, reggae-style song; band members insist it had always been known as their disco song and that they had created the sound by combining the influences of Kraftwerk and "Saturday Night Fever".