QUE CALIENTE.

Sales of Latin music rose twelve per cent over the past year--the only pop category to experience an uptick. Latin music, the industry term for Spanish-language records, owes much of its commercial vitality to three very different phenomena: RBD, a Mexican pop group whose members are actors on a popular soap opera; Shakira, a twenty-eight-year-old Colombian-Lebanese singer, who released albums in English and in Spanish this year and who performs in so many different styles that she is practically her own musical category; and, especially, reggaeton, the first genre in Spanish to become part of mainstream pop.

Reggaeton consists of rapping in Spanish over rhythms derived from Jamaican dancehall and salsa. These styles have existed for years, but until the nineties, when Puerto Rican artists began putting them together, Spanish rapping sounded like a stepchild of American hip-hop. Reggaeton turned the beat around. Rather than stressing the first pulse in every measure, the music accents offbeats, and the difference is evident on the dance floor: reggaeton speaks to hips, hip-hop to heads and shoulders. The music's syncopated movement suits the hard phonemes and quick cadences of Puerto Rican Spanish; the best reggaeton vocalists create long, complex musical patterns that are often more sophisticated than those of American rappers.

Hispanics, who two years ago overtook African-Americans as the largest minority group in the United States, may be the music's primary consumers, but this year reggaeton songs have begun to be played on pop radio, as well as on stations like Latino 96.3, in Los Angeles, which has adopted the Hispanic urban format, "hurban"--a mix of reggaeton and hip-hop. Hollywood has also discovered reggaeton; several films about the music are currently in development, including one funded by Jennifer Lopez's company, Nuyorican Productions.

The genre's most successful artist is Daddy Yankee, a twenty-eight-year-old Puerto Rican who, according to Nielsen SoundScan, has sold nearly a million copies of his 2004 album "Barrio Fino," mostly on the strength of a song called "Gasolina." Produced by Luny Tunes, two young Dominican men now based in Puerto Rico who are the genre's current trendsetters, "Gasolina" begins with spastic keyboard tittering, like an electrical circuit sputtering to life, followed by a crescendo of hammering drums--a common reggaeton motif. Then, as the beat and a meagre digital melody kick in, Yankee raps bluntly about a girl whose idea of fun includes turning on car engines. The chorus consists of a teasing call and response: Yankee chants, "A ella le gusta la gasolina" ("She loves gasoline"), to which a docile female chorus replies, "Dame mas gasolina!" ("Give me more gasoline!") Gasolina has been variously translated as "speed," "rum," "sperm," and, of course, "gas." The song is quintessential reggaeton: it hits the offbeat snares hard, and piles on sexual innuendo with manic energy.

Luny Tunes also produced "Pa'l Mundo," a new album by Wisin & Yandel, a pair of young Puerto Rican musicians who are among the genre's most accomplished. Wisin & Yandel tinker with reggaeton's formula, interjecting references to dancehall numbers and to the genre's Latin antecedents. A founding influence was the Panamanian artist El General, who scored a novelty hit in 1991 with "Muevelo" ("Move It"), an infectious song that combined Spanish vocals with dancehall's distinctively syncopated snare-drum pattern. El General's music was called "reggae en espanol," to distinguish it from Latin hip-hop, and in the mid-nineties, using a rhythm called Dem Bow, created by the Jamaican producer Bobby Digital, Puerto Rican rappers started rhyming in Spanish over dancehall, adding Puerto Rican slang and Latin percussion to the Jamaican template.

As a genre, reggaeton is where hip-hop was twenty-five years ago, slowly making the transition from dance singles and d.j.s to hit songs and stars. Like dozens of reggaeton numbers, Wisin & Yandel's single "Rakata" is addictive yet ultimately unsatisfying. The ...