The soundtrack to Elijah Wald’s book Narcocorrido is a very good introduction to the Mexican world of corridos — a kind of broadsheet ballad — and the incredibly popular narcocorridos, tales of drug smuggling, which outsell most Latin pop. But for all its dark side — lyrically it’s more akin to gangsta rap than anything else — the music is quite disarming, accordion-based polka like norteño music. The biggest emphasis is on the genre’s major band, Los Tigres del Norte, who kick-started it all in 1972 with “Contrabando y Traicion,” and who contribute eight of the tracks here, not only narcocorridos, but also more socially conscious work like “La Tumba del Mojado,” about illegal Mexican immigrants in the U.S. Some of the songs are quite deliberately violent and almost cartoonish, like “Las Monjitas,” by Grupo Exterminator. Some offer a different view of the drug trade, such as “La Chacalosa,” from narcocorrido’s biggest female star, Los Angeles-based Jenny Rivera, which brings in a brass band as accompaniment in a first-person tale of braggadacio. Lyrically, corrido becomes more interesting when it breaks out of the narrow confinement it’s giving itself these days — “Violencia en Los Angeles,” a ballad about the Rodney King riots, from Pedro Rivera (Jenny’s father). It has the topicalty which has always been corrido’s specialty, as does “El Circo,” with its allegorical message about Mexico’s PRI political party. As an introduction, this might be heavily weighted in the direction of Los Tigres (who, to be fair, have been dominant in corrido for many years), but with its eloquent bilingual liner notes, it gives the novice a great deal of information — and enjoyment.