Negro y Azul from the soundtrack of the 7th episode of the 2nd season of Breaking Bad. It opens by sampling Negro Y Azul, a narcocorrido ( a drug song ) by Los Cuates de Sinaloa, cowritten by Vince Gilligan, inspired by the events depicted in the series, also called the Heisenberg song
Here you can find a good interview with the band explaining http://blogs.amctv.com/breaking-bad/2009/04/los-cuates-de-sinaloa-interview/
World Music - the Music Journey 