Unnacompanied vocal music is probably the oldest form of music (as it doesn't require any instrument), present in all musical cultures. Vocal music may be wordless (for example, onomatopoeic or improvisational), or feature text (lyrics). Unnacompanied vocal music is often reffered to as 'a capella', a term which means 'as in the chapel'. This comes from the 19th century notion that Renaissance polyphonic music was performed in an unnacompanied manner (it is now believed that parts were actually doubled by instruments).