Most of the carnival street parties in Rio are organized and run by Blocos. Each Bloco consists of a musical band and a group of partygoers. The Blocos, closely linked to the neighborhoods they come from, start their free-to-join parades early in January and continue throughout the carnival season. Playing usually their own samba song, backed up with a numerous bateria (drum and percussion players), Blocos are considered the beating heart of the Rio Carnival.