The chocalho is basically a shaker on steroids. It fills the part of a regular shaker, but where a standard shaker would struggle to be heard amongst the noise of the bateria, the chocalho can easily hold its own. 

Often underrated, the chocalho is one of the most valuable instruments in the bateria. When played well, the chocalho delivers like a freight train of swing injected right into the bateria. As much as any instrument, it delivers the power and the rhythm that sustain the band and makes people dance. It is a very satisfying instrument to play.

The chocalho is not technically difficult, but it does require a good sense of tempo, not to mention stamina to be played well. It can be quite a workout playing the chocalho for an extended period, but the best players use very efficient playing techniques to conserve energy.

The chocalho also has the great advantage that it is generally on or off. There aren't as many complicated sequences, patterns and breaks to remember like there are with most of the other instruments. This makes it the perfect instrument if you're inclined to play with several samba bands, and can't necessarily remember the finer points of all their rhythms and breaks!

To see the kind of power the chocalho brings to the bateria, check out this video of a Grande Rio Bateria warm up, where you can see the chocalho section front and centre.