Was a question in a comment on my last post.
Here is a video clip of the technical practice in 2011 of the bateria (drum section) of the Samba School Mancha Verde (green stain).
The guy in front with the whistle (no batons here) is the Mestre (conductor); they can get quite animated. Some schools have two baterias.
Video clip by Camila Miniusi – Thiago Gomes Tamborim