If you go to enough concerts, it’s bound to happen to you every now and then: the programme includes a work that you weren’t particularly looking forward to, and the performers blow you away, utterly transforming your view of the piece. In this case, the performers were Camerata Bern and the work was Bartók’s Divertimento for strings.

I have to confess to being rather hit and miss with Bartók: sometimes I get it, sometimes I don’t. I listened to a recording of the Divertimento a couple of times before coming here and it left me completely cold. I wasn’t the only one: my next door neighbour was muttering things about not being too sure about the Bartók and hoping it would be OK.

Camerata Bern’s playing was a revelation. I found myself constructing an inner narrative about the piece: the composer is trying to write a light hearted divertissement but is continually interrupted by fears and inner demons, which keep rising to the front of the music: the composer bats the demons away but they keep returning. As the work progresses, particularly in the second movement, the anguish ratchets up. This is a piece of music written by someone very, very frightened about the future, and since the work was written in 1939, the fear was well founded.

What made the performance so fantastic was the vitality of the happy components juxtaposed with the searing power of the interruptions in a variety of a dozen different textures, ending with an extraordinary pizzicato section. These qualities come from musicians absolutely at the top of their game playing with total togetherness and confidence in each other. The audience was mesmerised; the doubters (my neighbour and I amongst them) totally converted. Maybe there was something in the air: Bartòk composed the work in a house around 50 metres from Saanen church, during a visit to Gstaad.

The concert started with the Bach double violin concerto. This could not have been more different from the three Bach concerti in this same church the previous evening, in spite of being played by a similarly sized ensemble. Camerata Bern play on modern instruments with a string lineup including three violas, two cellos and double bass, compared with I Barocchisti’s period instruments and just one viola, one cello and viola da gamba. Both ensembles were excellent in following Bach’s contrapuntal lines, but where I Barocchisti were delicate and precise, Camerata Bern were vivid and muscular.

The first movement of the double concerto is strangely un-concerto-like, so subtly are the solo parts blended in to the orchestral whole. The slow movement is more conventional: a beautiful, dreamy melody passed from one soloist to another. The rapport between Camerata Bern’s director Antje Weithaas and her co-soloist Meesun Hong was wonderful to watch: the pair obviously really enjoy playing together. This was especially evident in the joyous third movement, in which their energy and enthusiasm infected the whole ensemble and the audience with it.

So everyone had pretty much already got their money’s worth when the star act of the evening arrived: Katia and Marielle Labèque playing a concerto that Mozart originally wrote to play with his sister. The spooky thing about hearing the Labèques play is that if you shut your eyes, you’re utterly convinced that there’s only person there. Clearly, your brain tells you, it must be impossible for two people to play that precisely together. The effect was particularly extraordinary in an extended trill in the third movement where the force of two pianists so perfectly in sync was overwhelming. As well as all that precision, the Labéques play Mozart with a rare delicacy: a warming, gentle treat after the angst of the Bartók.

For encores, the Labèques let their hair down: a Bernstein Jazz number (high speed boogie woogie, only not quite straight) was played with gusto and great merriment, followed by them joining together on one piano for something schmaltzy and French-sounding I didn’t recognise. It brought a huge smile to everyone’s lips and closed off a thoroughly memorable evening’s music.