Absorbing documents these, though the magnetism is less in the music than in the men who made it. Indeed, you couldn’t ask for three more diverse masters of the rostrum. Bruno Walter is captured both in rehearsal and in English-language interview, where he insists on moral fibre as a vital extra-musical qualification. Those familiar with his recorded rehearsal of Mozart’s Linz (Sony) will anticipate the humanity, the patience and the pleading emphasis on espressivo playing, sometimes when specifically marked, at other times implied by written dynamics. Picture quality is OK-ish and the sound adequate, good enough to capture some accomplished playing by the 1958 Vancouver International Festival Orchestra.

We hear rehearsals for the first and fourth movements of Brahms’s Symphony No 2, Walter urging his players to sing, pausing now and then to clarify a point of articulation. There’s not much use of metaphor, just a confident hand and a warm heart, the impression of favoured territory gratefully revisited, the face, with its strong features and powerfully expressive eyes, amazingly photogenic. A split-second glance from Walter was enough to tell you all you needed to know.

By contrast, Carlos Kleiber in 1970 is at constant pains to explain mood, atmosphere or the finer subtleties of tonal shading. In Weber’s Der Freischütz Overture, he conjures images of ghostliness and rapture, of darkness and light, both in terms of eloquent verbal description (subtitles are provided) and vivid gesture. His powers of suggestion exceed those of any other conductor in my experience, extending to musical timing, the tiniest nuance and to such concepts as danger, wonderment or dread. Time and again a passage repeated means a passage coloured, intensified or brought into clearer focus. Players from his Stuttgart orchestra nod in recognition as a point freshly hits home, though ‘hits’ is perhaps the wrong word for a conductor whose consistent politeness and dedication inspire a wholehearted response. Kleiber laughs and jokes, rather shyly at times, becomes boyishly over-excited, frets visibly when he fails (or thinks he fails) to focus an idea correctly and beams like the sun whenever all goes well. He’s as much an inspiration to watch as to hear (both aspects fairly well catered for on this nicely produced DVD), a force of nature who in Strauss’s Die Fledermaus Overture recognises untold shades of musical meaning. Everyone who watches Kleiber stands to learn something valuable.

With the ‘discophobe’ conductor Sergiu Celibidache, you can’t but help learn, though the value of his teaching is perhaps more open to debate. Both Walter and Kleiber promote, in their very different ways, an intelligent musical balance of assertive argument and repose, but the ageing ‘Celi’ seems obsessed with unstitching textures to lay bare every musical thread and tendon. He demands space, time, selfless attention (his manner with students sometimes verges on mental cruelty) and patience. Celi tends to talk in riddles and metaphorically dismisses any commentators who accuse him, probably rightly, of dictatorial behaviour. And although this mighty alchemist demands respect – his Bruckner remains phenomenally compelling – you get the distinct impression that he’s playing games, teasing or testing people, working out who he can or cannot trust.

We see him teaching; we hear him conduct Bruckner, Bartók, Haydn, Schubert, mostly as analysed in rehearsal, and we watch as he wanders through his garden watering the plants, feeding the birds or walking into the wooded distance with his wife. But while Walter makes the marriage of nature, spirituality and music seem like good old-fashioned common sense, Celi (via his director-editor son, Serge Ioan) transforms that same marriage into an almost unattainable goal. I’d loved to have been a fly on the wall in student halls after the lessons, though I doubt that in retrospective anyone present would have willingly missed out on the experience. Good sound and picture quality.