This year's Sommets Musicaux is all about the harp, so they could hardly have found a more appropriate headline act than Emmanuel Ceysson, a young harpist who exudes love of his instrument from every pore. Ceysson is simply great to watch, not least for his boyish enthusiasm: whenever he executes a glissando or some other complex move, a big smile lights up his face as if to say “how great is it that I can make my instrument do this”.

And indeed, Ceysson played the Glière concerto with tremendous virtuosity. To the untutored eye, the harp looks like a fiendishly difficult instrument at the best of times – you’re being asked to play an awful lot of notes on a set of strings that doesn’t really look as if it’s laid out terribly congenially – but Ceysson is clearly at the level where he can not only play these complex phrases but can accelerate into them or slow them down mid phrase or alter the dynamics to suit the particular mood.

But for all Ceysson’s virtuosity, this wasn’t a vintage concerto performance, for the simple reason that conductor and orchestra weren’t really in sync with their soloist. Under the baton and watchful eyes of Ondrej Lenárd, the Prague Radio Symphony were producing plenty of energy, but there were many places – pretty much everywhere in which soloist and orchestra weren’t alternating – in which the harp was difficult to hear.

Listeners could be forgiven for not spotting the harp link in the first work on the programme, Schubert’s well loved Ave Maria. Schubert’s original is a setting of a prayer from Sir Walter Scott’s The Lady of the Lake, which is accompanied by the far-away playing of the harper Allan-bane. Inva Mula chose to sing the Latin prayer rather than Schubert’s original words (a loose translation of Scott), which she did with authority and purity of voice: Mula has a strong soprano and was able to project real reverence.

But here also, it was not clear that the orchestra were really at one with their soloist – or even with each other. It wasn’t until their third piece, the second of two of Dvořák’s Legends, Op.59, that I started to feel that the orchestra were secure enough to be able to add some lilt and sway to the music, with wind quotes lifted nicely out of the background strings.

After the Glière concerto, Mula returned to sing Rachmaninov’s Vocalise, followed by the Song to the Moon from Dvořák’s opera Rusalka (which has a prominent and romantic harp part in its orchestral accompaniment). These are both wonderful pieces capable of being very expressive; and expression is what Mula gave them, singing highly theatrically and clearly able to command the notes and sing them with excellent technique.

Mula was particularly notable for the sheer amount of emotion injected into the Song to the moon. She is able to sing with complete legato in all parts of her register, and the low near-desperate phrases just before the end contrasted well with the fervency of the preceding prayer and the highs of the chorus. Mula may, however, have misjudged the room: she has a huge voice which would fill most opera houses (I’ve reviewed her being quite successful in filling an outdoor open arena) and was seriously overpowered for the modest size of Saanen Church. This was particularly noticeable in the impressive vocal fireworks of an encore that she played together with Ceysson, a Czech song called The nightingale.

In sum, therefore, a programme of beautiful music and a pair of fine soloists, but a concert somewhat let down by a lack of rapport between soloists and orchestra.