EDIT :
Let's see:
- What are the styles/main grooves played by Brazilian samba drum ensembles?
Thinking in terms of percussion, do a Youtube search for "enredo escola de samba". Enredo is the story that the Samba schools sings, dance, homage during the carnival. It may be based on some folkloric history, real history, a person, the Samba school it self.
I believe that the "drum lines" are relatively the same, except for the transitions and such. Rio de Janeiro's carnival is one of the biggest events in our country (I don't like it, personally).Famous Samba schools includes: Mangeuira, Beija-Flor, Salgueiro, etc...
- Can you give me examples of them? (either by video, or by rhythm
sheet)
The videos speaks for themselves. The Bateria (drums) is one of the most important categories and if they screw-up, it may cost the "Championship" for the school. As you'll see in the videos, the whole crew makes up the vibe. The costumes, the allegory, SFX, even the crowd. This video is a compilation of 50 songs, the uploader claims to be the all time Top 50.
- Where can I learn about how these styles are constructed? (Main and counter rhythms, using accents, how do they do deviate from straight, "Western" feel, which makes up the groove, what is essential in recognizing the groove, where you can "play" with the rhythm)
Though question. If you ask this to a member of the bateria he'll probably claim that you either "have it" or not. I can stress enough how complicated and yet simple Samba is. Is all about swing, knowing your timing, improvising. As we say here, you gotta have the manha (the only translation I can think of is "craftiness"). So, watch the videos, see how they "don't care" about keeping tempo, time signature, and yet they know exactly what they're doing. I believe that it all sums up to: Have fun.