A radio documentary or feature is a purely acoustic performance devoted to covering a particular topic in some depth, usually with a mixture of commentary and sound pictures. It is broadcast on radio or published on audio media, such as tape or CD. Some radio features, especially those including specially composed music or other pieces of audio art, resemble radio drama in many ways, though non-fictional in subject matter, while others consist principally of more straightforward, journalistic-type reporting – but at much greater length than found in an ordinary news report.