Britten was now composing lots of music: songs, chamber music and a very popular piece called "Young Person’s Guide to the Orchestra" (also known as "Variations and Fugue on a Theme of Purcell"). This piece shows off each instrument of the orchestra in turn so that young people can get to know the sound of the musical instruments. It is based on a tune written by Henry Purcell 300 years ago. There were more popular works: St Nicolas and the Spring Symphony. There were not many opportunities for big operas to be performed, so he wrote some “chamber operas” which only needed small orchestras and a small number of singers. These were performed in places such as local churches by a group which called themselves English Opera Group. He wrote "The Rape of Lucretia" (1946) and "Albert Herring" (1947). In 1948 the group helped to start a music festival in Aldeburgh. Benjamin Britten spent the rest of his life mainly working on music which was to be performed at the Aldeburgh Festival. He composed some of his greatest works for the festival, and he took part in the performances as conductor and pianist.