I believe it sounded like a cross between pop and heavy metal, but I could be wrong. The reason that the clapping was so memorable is that it sounded out of place in its style. Remember: it occurs ONLY in the measure before the chorus. It begins on the downbeat: 1 CLAP, and CLAP, 2 CLAP, and CLAP, 3 REST, and CLAP, 4 CLAP, and REST. It is never stated except once each time.