Kristjan Järvi cuts quite a dash on the podium, youthful, exuberant and full of energy, all adjectives that could be applied to the music in last night's Barbican crossover gig by the LSO, entitled "Balkan Fever". The concert was in two halves, linked by an over-arching theme of folk- and gypsy-inspired music, the first half being straight classical (Kodaly and Enescu), while the second was headlined by the Theodosii Spassov Trio. Spassov is a Bulgarian player of the kraval (an end-blown flute); he is accompanied by two guitarists.

The programme's concept was to start with the more refined classical pieces and then to look at other things that have grown from the same musical roots. Accordingly, we started with the elegant tones of Kodaly's Dances of Galánta with its haunting solo clarinet part and lush backing of strings and horns. It's a varied and exciting piece, with plenty of melody and plenty of different rhythms, and I was struck by the LSO's high quality of individual playing. The solo woodwind parts are extremely prominent, so the principals have to be good - and they were, beautifully phrased and tightly in time with the rest of the orchestra - most notable was Chris Richards on clarinet. And although this wasn't a Strauss or Mahler-sized orchestra, the string sound was full and rich.

Järvi was certainly animated and throwing energetic body signals at the orchestra, but not with the effect I might have expected: the slow passages sounded suitably gorgeous, but the faster dance rhythms seemed rather leaden, and I imagined dancers struggling to really lift their feet and fly. This improved as we went into the second Kodaly work, his Variations on a folksong "The Peacock". Although neither entitled "dances" nor a "rhapsody", this had an overall feel that was rather rhapsodic and contained many clear dance rhythms. It was easy to listen to and energetic, but perhaps a shade long for the material: I wasn't able to concentrate for the whole piece. The first half closed with Enescu's Romanian Rhapsody no. 1, which upped the energy yet again: after a gentle, elegiac opening (again, strongly featuring the clarinet), the work picks up some really high speed and some neat orchestral effects, including one notable trick of an up-then-down scale spanning several octaves by being handed smoothly across several instruments. By now, the LSO seemed to have found their rhythmic feet and the accenting was clear as we moved between various dances and marches.

I didn't really know what to expect from the Theodosii Spassov Trio, but it certainly wasn't what we got. My first feeling was of being at the opposite end of Europe in southern Spain, as guitarists Vlatko Stefanovski and Miroslav Tadić gave us a virtuoso showing of a jazz-flamenco style which reminded me most of the guitar trio of Paco de Lucia, Al di Meola and John McLaughlin: flowing lines and very fast rolling finger picked accompaniments. All three musicans are technically impressive and thoroughly eclectic in taste: as well as the expected Eastern European and gypsy influences and the unexpected flamenco, I could hear snatches of the Middle East, South America and other places. All of this was done with gigantic verve and energy, with the LSO clearly enjoying themselves: I could see the side drum player grinning from ear to ear in one piece where a heavy basic rhythm was overlaid with accenting too complex for me to tap feet with but whose timing definitely involved a lot of prime numbers. Spassov himself is an extraordinary performer, given the relatively primitive nature of his instrument, his technique including singing into the flute, blowing into all sorts of holes that weren't the main mouthpiece and even a bit of beatboxing.

The LSO presumably hoped to appeal to two audiences – their usual classical audience and the fans of jazz/folk/world music (including London's Eastern European contingent) – and given the packed hall, they obviously succeeded. It's harder to know what the two cohorts made of each other's music: from the general reaction, my guess is that each quite enjoyed the other but probably wouldn't have wanted any more of it. Having a foot in both camps, I felt that way about both. The classical half contained some thoroughly enjoyable music, but with three very similar pieces, while the kind of jazz-folk done by the Spassov works better in a more relaxed environment than a standard concert hall.

Fever? Certainly, with tons of energy throughout the evening. Balkan? I'm not so sure. Neither Kodaly or Enescu were from the Balkan peninsula, and the Spassov Trio is far too cosmopolitan to be pinned to any particular place. But a pleasant, escapist evening's music none the less.