Such large instruments are usually played by several marimbists, each player responsible for a particular register, within the confines of which he is obliged to stay. In addition, instruments with three or four octaves are also used. The resonators are often made of bamboo. Marimba ensembles with several instruments are a notable tradition which is still followed today, especially in Mexico City and Chiapas; a group of musicians plays on one marimba or several. In Europe, Japan and the USA marimbas are played almost exclusively by soloists.