Reggaeton's signature sound, and the thing that distinguishes it from Latin hip-hop, is a tripping, polyrhythmic drum track derived from the Puerto Rican dance music bomba. Most songs still use some version of it, though the naturalistic instruments have long since been distorted and pixilated in the studio by reggaeton producers like Luny Tunes.

Their most recent compilation, Mas Flow 2, is a good primer for the uninitiated since it includes appearances by most of reggaeton's stars. By far the biggest of these is Daddy Yankee, who had the best-selling Latin-music album in America last year (Barrio Fino) and can lay claim to two of the genre's biggest hits, "Machete" and "Gasolina." Other essential songs include "Reggaeton Latino," by veteran Don Omar, which enjoyed modest airplay on MTV, and "Guasa Guasa" by Tego Calderon. With his drowsy baritone flow, Calderon straddles the line between reggaeton and hip-hop and has produced several high-profile collaborations with American rappers, including The Game ("We Don't Love Them Hoes") and Cypress Hill ("Latin Thugs").

But it was Queens-born rapper Noreaga who scored the genre's first mainstream crossover hit in the fall of 2004 with "Oye Mi Canto," a bouncy club anthem in which he trades Spanglish verses with Daddy Yankee and claims first-mover status for himself: "It's the first time it's ever been done/because there's never been/a rapper doing a reggaeton album/and he's a veteran," he raps.