Samba is a musical genre and dance style with its roots in West African traditions brought to Brazil via the slave trade. It developed in the favelas of Rio de Janeiro. Samba is characterized by a strong 2/4 rhythm and a syncopated beat. The heart of Samba is the 'Bateria' (percussion section), which features instruments like the surdo (large bass drum), caixa (snare drum), tamborim, and the agogô (metal bells). One of the most unique instruments is the 'cuíca,' a friction drum with a bamboo stick tied to the drumhead inside the shell; the player rubs the stick with a wet cloth to produce high-pitched squeaks and grunts. Samba became the symbol of Brazilian national identity in the 1930s. During Carnival, 'Samba Schools' (Gres) compete with massive parades featuring hundreds of drummers. The style has branched into many subgenres, including the slower, more melodic Bossa Nova.