Salsa music always has a 4/4 meter. The music is phrased in groups of two bars, using recurring rhythmic patterns, and the beginning of phrases in the song text and instruments. Typically, the rhythmic patterns played on the percussion are rather complicated, often with several different patterns played simultaneously. The clave rhythm is an important element that forms the basis of salsa. Apart from percussion, a variety of melodic instruments are commonly used as accompaniment, such as a guitar, trumpets, trombones, the piano, and many others, all depending on the performing artists. Bands are typically divided into horn and rhythm sections, led by one or more singers ("soneros" or "salseros") .