The rhythm section members sometimes break out of their accompaniment role when they are asked to perform keyboard solos, bass breaks, or drum solos. In genres such as progressive rock, art rock, or progressive metal, the rhythm section members may play complicated parts along with the lead guitar (or vocalist) and perform extended solos. In jazz groups and jazz fusion bands, the rhythm section members are often called on to perform improvised solos. In jazz, the drummer may "trade" short solo sections with a saxophone player or trumpet player; this practice, nicknamed "trading fours", typically involves the drummer and the horn player alternating four bar solo sections during a jazz tune. They can also trade eights, twos, ones, or other numbers depending on the musical context.