The opera was started to be recorded in stereo, but it seems that the reason it ended up in mono only was due to Fischer-Dieskau and Wächter: apparently they had disagreements about where their microphones would be placed or who would have more microphones (and therefore who would be better listened). a ridiculous matter of egos, and thanks to that ridiculousness, Legge made the decision to end the recording only in mono, in order to keep the party peaceful and avoid major setbacks.