Drum percussion encompasses any musical instrument—specifically membranophones (drums with a stretched head) and idiophones (self-sounding objects)—that produces sound by being struck, shaken, or scraped. They provide the foundational rhythmic pulse, energy, and texture in nearly all musical genres and traditions worldwide. The percussion family is believed to include the oldest musical instruments.Percussion is commonly referred to as "the backbone" or "the heartbeat" of a musical ensemble, often working in close collaboration with bass instruments, when present. In jazz and other popular music ensembles, the pianist, bassist, drummer and sometimes the guitarist are referred to as the rhythm section.Percussion instruments are classified by various criteria sometimes depending on their construction, ethnic origin, function within musical theory and orchestration, or their relative prevalence in common knowledge.