Despite this, the use of vibrato in late Romantic music is still common, though challenged by Roger Norrington and others of the historically informed performance movement. Performances of composers from Beethoven to Arnold Schoenberg with limited vibrato are now common. Norrington caused controversy during the 2008 Proms season by conducting Edward Elgar's Enigma Variations, and the Last Night of the Proms, in non-vibrato style, which he calls "pure tone". Some take the view that even though it may not be what the composer envisioned, vibrato adds an emotional depth which improves the sound of the music. Others feel that the leaner sound of vibratoless playing is preferable. In 20th-century classical music, written at a time when the use of vibrato was widespread, there is sometimes a specific instruction "not" to use it (in some of the string quartets of Béla Bartók for example). Furthermore, some modern classical composers, especially minimalist composers, are against the use of vibrato at all times.