Precious mementos here – including the so-called ‘bonus’ tracks. But why, will anyone tell me, are they ‘bonus tracks’ at all? They are comparable in interest, importance and length to the so-called ‘main menu’. Elisabeth Grümmer is a soprano of whom we all want to hear as much as we can, and Elsa was one of her most admired roles. Wolfgang Windgassen was the best singer among the Wagnerian tenors of his time, and Gottlob Frick was the incomparable bass. These three substantial excerpts from Parsifal are a bonus indeed, but why should they be accorded the anomalous status and have to be accessed separately?

Of course, all of these items filmed between 1958-68 have limitations, particularly of visual quality (close-ups are in excellent focus but longer shots tend to be fuzzy). The great thing is that something of each artist is captured which goes beyond sound-recording, and, for those who saw and heard them in the flesh, helps recall them to the mind’s eye and for a new generation may give a living presence to a name and a face and a body to a voice.

The first of them, for instance, Gundula Janowitz, is beautifully brought before us, the patrician quality of her singing so at one with the dignity of posture and expression and both incorporating a warm humanity always ready to reward with smiles. Gobbi, seen in four vivid scenes, is the master of make-up, of the rolling eye and the arched eyebrow – but more, for he stamps every phrase with its special timbre. Christoff is greatness itself in the rightness of movement and expression: we never question anything this Boris Godunov does, not even when under the camera’s unsparing eye. And with all these, there is never any question – essentially they are great singers. Right from the start, Janowitz in the clean ‘take’ and caressing curve of Agathe’s ‘Wie schön die Nacht’, Gobbi in the rich vibrancy of his ‘taveniere’, Christoff from the unforgettably personal quality of his resonant commands, all have the voice as their essential source of identity.

Rita Streich is not heard as favourably: the recording catches an edge, and I don’t like (but can’t help) watching for that shaking jaw on the high A flat. The DVD comes without anything beyond the bare facts of who, where and when. The English subtitles are helpful.