One of Callas’s greatest nights in the theatre is also, unfortunately, one of Warner’s worst transfers. This sounds very much like the old EMI, which was transferred from a very poor source. The sound is muddy and apt to wander in pitch. You just have to listen to Divina’s wonderfully clear, clean and crisp version to hear the difference.
I reviewed the performance in its Divina transfer back in June last year, and, rather than just repeating myself, would enjoin you to read my review by clicking on the following link https://tsaraslondon.wordpress.com/2017/06/13/anna-bolena-la-scala-milan-april-14-1957/