The Second Viennese School was a group of composers made up of Arnold Schoenberg and those who studied under him in early 20th century Vienna. Their music is characterised by atonalism and Schoenberg's twelve tone technique. The principal members of the school were Alban Berg, Anton Webern and Schoenberg, although there are lesser known composers who ought to be covered by the term, such as the Greek Nikolaos Skalkottas.
The first Viennese school, which is rarely referred to as such except in comparison to the Second Viennese School, is generally taken to consist of composers working in the late 18th and early 19th century, particularly Wolfgang Amadeus Mozart, Joseph Haydn and Ludwig van Beethoven.