Whatever the historical realities of Bach’s day, performers will always seek to find solutions which can heighten the impact of great music. Here, it is a 1953-54 set of unaccompanied Bach in which the ‘Vega’ (from maker Knud Vestergaard) bow allows the tension of the bow hair to alter according to whether the music is essentially chordal or melodic. The most striking effect is that the usually ‘awkward’ spread chords sound simultaneously and easily like a quasi-keyboard or harmonica. Purists may shudder but we’d do well to remember that expressive nuances of all kinds (such as the extent of vibrato or the nature of portamento – to name but two) have evolved to form an unavoidable part of an historical consciousness, beyond our knowledge of ‘original’ practices. There is, understandably, an experimental air to the earlier recordings in the collection, even a caution in the slower movements. Yet the expected technical challenges of the tuning, timing and placement of chordal passages appear here as rarely heard before and allow one to appreciate Bach’s grandeur of conception in an often extraordinary, if strangely ephemeral, way.

The violinist here, Emil Telmányi, was the one-time son-in-law of Carl Nielsen and an accomplished player in his own right. Curved bow or not, it still takes outstanding playing to render these works convincingly and Telmányi’s approach is one based more on the seriousness of a Joachim than the relative showmanship of Sarasate. His style is a curious amalgam for the 1950s. Portamenti are still unashamedly employed, as in the Grave in the A minor Sonata, and yet he is also clearly in the thrall of the new geometric leanings of neo-Baroque articulation which pervaded Baroque music in the 1930s and ’40s. The B minor Partita is uncomfortably short in the flexibility and vitality of Joachim (the Tempo di Bourrée is a comparative dirge) with too much hard hitting and metronomic staccato in the fast movements.

The D minor, on the other hand, bubbles with characterisation and lightness of touch; his technical handling of the bow is far more assured and the Ciaconna is delivered with a pleasing richness of timbre even if the plentiful chords, with their slackened bow tension, often seem impersonally to scream out of nowhere. This, for me, is the ultimate shortcoming of this bow vogue. Yes, a better hit rate on the hard chords of the C major Fugue and the E major but a crucial loss of that gloriously organic and often febrile engagement where harmony is created out of the same belly as melody, both implied and real. The low-tension bow, not unsurprisingly, leads to lower tension all round as melody and harmony part company. That’s just the start of it as the interpretation can only operate within its given technical parameters. You can hear Telmányi thinking about the chordal music as a series of peaks to be negotiated, but not knowing what the air smells like down there. The same sensation occurs in Rudolf Gähler’s glutinous 1998 set, which also employs a curved bow but has none of Telmányi’s grace.