Half speed mastering.
 
A Night at the Opera is the fourth studio album by the British rock band Queen, released on 21 November 1975 by EMI Records in the United Kingdom and by Elektra Records in the United States. Produced by Roy Thomas Baker and Queen, it was reportedly the most expensive album ever recorded at the time of its release. The album's title is taken from the Marx Brothers film of the same name.
 
EMI - 00602547202697