Solti's Bayreuth Ring* (his first I think) had a making-of made as a feature of its own.
A film team officially accompanied the production and the rehearsals. Something quite uncommon at the time. In addition there was an audio feature using the recordings to explain Wagner's leitmotif technique in detail.
*that's where the clip comes from if I am not mistaken
Solti's Bayreuth Ring* (his first I think) had a making-of made as a feature of its own.
A film team officially accompanied the production and the rehearsals. Something quite uncommon at the time. In addition there was an audio feature using the recordings to explain Wagner's leitmotif technique in detail.
*that's where the clip comes from if I am not mistaken