I don't know much about murga yet, but I am intrigued. It first began when I heard this song, "Cumbia Murguera," by Chancha Via Circuito, the Argentinean musician:
The sound reminded me of something, but I couldn't say what. Then I was reading an article/interview with him (I forgot where and I can't find it now) where he mentioned that having played the drums in the murgas of his hometown as a child was formative in his musical development.
According to Wikipedia, murga is a form of popular theater. But it seems the Argentinean style - which differs from the Uruguayan style (murga originated in Uruguay) - features less vocals. There is a lot of percussion, and a lot of dancing.
Watch this 10 minute montage of Murga Porteña (Buenos Aires-style Murga) - carnivalesque marching band, Argentine-style.
And this low-budget street murga. Watch the way they kick, and the little kid, and they way they rock the little cymbals atop their great drums - especially at the end.