In the heyday of George Szell’s tenure as its chief conductor, The Cleveland Orchestra had few if any peers among the world’s great orchestras. That it remains one of Western music’s classier acts is due in part to that heritage, in part to the quietly effective curatorships of Christoph von Dohnányi (1984-2002) and Franz Welser-Möst, who will have completed 20 years with the orchestra when his current residency ends in 2022. Yet Welser-Möst himself remains something of an enigma; and it’s an enigma we have plenty of time to ponder during the six and a half hours of video footage that make up this extended Brahms edition, filmed live at home in Cleveland and on tour in London and Vienna in 2014-15.

Now in his mid-fifties, Welser-Möst’s podium manner remains that of a shy but dutiful conservatoire student: the immaculately executed beat, the largely redundant left hand, the frequent furtive glances at the printed score, the somewhat marionette-like stance. What matters, of course, is what goes on in rehearsal, and the exemplary levels of concentration generated in performance by his superlative musicians. When a Viennese critic writes of two of these Brahms performances ‘glowing from within’, something must be going right. As indeed it is in what is a lyrical and in the end surprisingly fiery account of the Second Symphony.

There is also much to be said for Welser-Möst’s Boult-like circumspection in the First Symphony. I have long felt uneasy about Brahms cycles in which the First Symphony explodes on to the scene like some musical King Kong. Welser-Möst’s creature is fleeter of foot and a good deal less threatening. ‘Beethoven’s Tenth’, folk used to joke. What Welser-Möst gives us is more like Schumann’s Fifth.

It is in the slow movements and the fluidly realised third-movement intermezzos that Welser-Möst’s readings give the greatest pleasure. Which may explain why the First Symphony, with its scherzo-like first movement and loosely evolved finale, works, where his account of the tragic Fourth Symphony – here more a jaunt than a journey – self-evidently fails.

His account of the Third Symphony is also sadly underpowered. You could put this down to the prissily disengaged nature of the beat. (Who was it – Furtwängler, Boult? – who said there is no more difficult symphony to start, such is the orchestral mass which has to be hoisted aloft.) But I suspect that’s only part of the story. Compare this performance with Szell’s 1964 Cleveland recording (Columbia, 8/65 – nla) and, though Welser-Möst’s tempi are generally quicker, they seem slower because the rhythms are less tautly drawn, less powerfully energised from within.

Welser-Möst often seems more energised – and more completely himself – when there is a soloist to hand. Julia Fischer delivers a richly concentrated account of the Violin Concerto, finely accompanied, and Yefim Bronfman is a solidly reassuring presence in the two piano concertos. Again, slow movements are a highlight, not to mention a beautifully articulated account of the B flat Concerto’s skittish and all-too-elusive finale. Only in the finale of the D minor Concerto does the music-making take on an uncharacteristically dishevelled air, as spur-of-the-moment excitement takes hold.

As to the set’s technical qualities, the BBC’s Proms relay of the First Symphony is in a class of its own, superior in sound quality to that achieved in the Second and Third Symphonies recorded in Vienna’s Musikverein by the French Mezzo channel, and superior to most of the home-grown footage generated by Cleveland’s local provider, WVIZ/PBS ideastream. In the piano concertos, it is the Cleveland team’s inconsistent and occasionally eccentric video direction that is the problem; in the violin concerto it is the closeness with which Julia Fischer’s admittedly riveting playing has been recorded. As for Welser-Möst’s daring emphasis on the crepuscular colours in which Brahms dresses the theme of his St Antoni Variations (oboes pitted against bassoons, contrabassoon, low horns, cellos and double basses), this is completely missed by the video director.

The DVD booklets are none too thorough either. They lack movement timings and are silent on such matters as the identity of the cadenza used by Julia Fischer in the Violin Concerto. In case you are wondering, it is the Joachim.