A "jazz standard" is a musical compositions which is an important part of the musical repertoire of jazz musicians, that it's widely known, performed, and recorded by jazz musicians, and widely known by listeners. Well. 'Round Midnight, by pianist Thelonious Monk is one of the great jazz standards. In this video you can see Monk with his quartet (do not miss the piano solo from 4:00 minute).
Thelonious Monk - 'Round Midnight