The (to date) 11 released recordings of Hans Knappertsbusch’s Parsifal performances at Bayreuth between 1951 and 1964 constitute a unique record of one conductor’s work on a favoured score in a single theatre. By 1942 “Kna” had logged up over 90 performances in a number of venues of a work he first led when he was 25, but after 1951 he would only conduct it in Bayreuth. Technical gremlins in Bavarian Radio’s transmission of the 1964 first night led to its being replaced by a recording of the present performance, the last night of the run. It was not only Kna’s last ever Parsifal, it was to be his last ever public performance.

Thirteen years of performances saw changes to Knappertsbusch’s shaping of the score which were as subtle but as continuous as those taking place in the seminal Wieland Wagner stage production which it accompanied. Compare the original 1951 recording (Decca, now Naxos): if the basic tempi remain slow, the pulse is much more sharply defined and the much-commented weight has been replaced by a colourful plasticity which is almost Debussian. Also, rather like an extended version of Walkure Act 1, there is now only one real climax in the whole interpretation. “Be off with you now and let’s have a good Good Friday Spell”, the conductor apparently told Hans Hotter in an interval conversation – and they did, with a monumental strike (shattering timpani, shining brass, thrilling precision from Gurnemanz) at the launch of the scene on the holy meadow.

The performance is also vital for its preservation of Jon Vickers’s Parsifal. In his second appearance on the Green Hill the Canadian tenor mixes great strength and great beauty of voice to an almost platonic ideal in the tricky Act 2 dialogue with Kundry. Here what can sound like sermonising becomes passionate, convincing rhetoric. Hotter’s Gurnemanz, in its range of inflections and illuminating line readings a close cousin of his Wotan, has ripened too since the widely circulated Philips reading of 1962. Thomas Stewart took over Amfortas this year from George London, reaching frightening heights of persecution mania in his last confrontation with the brethren in Act 3.

As with the predecessors in their “official” Bayreuth series, Orfeo has denied us some of the “live” atmosphere with its scrubbing and cleaning up of the original radio recording. It is also transferred at rather a low volume. However, forced into a ridiculous choice between “Kna” Parsifals, I would now set this alongside the 1954 version (Archipel, his return to the Green Hill after an enforced year off) as the ranking interpretations from this maestro.