Mexican crooners sing about drug cartels, and sometimes find themselves the victims of violence.The story of a drug cartel hood who dissolved the bodies of 300 victims in acid might dominate news reports and then R-rated movies. But in Mexico, it is also the subject of popular songs. Santiago Meza, a 45-year-old who confessed last week to the grisly work he committed for crime bosses over the last nine years, is revered in lively ballads with names such as “The Cook.” “I have got many women, and I make a lot of money, because I am a specialist, the best...