Yoruba music includes songs of ridicule and praise, as well as lullabies, religious songs, war songs, and work songs. These usually follow a "call and response" pattern between a leader and chorus. Rhythm is provided by drums, iron gongs, cymbals, rattles, and hand clapping. Other instruments include long brass trumpets, ivory trumpets, whistles, stringed instruments, and metallophones. Perhaps the most interesting musical instrument is the "talking drum." The "talking drum" features an hourglass shape with laces that can be squeezed to tighten the goatskin head, altering the drum's pitch.