If three years is sufficient to constitute a tradition then, traditionally, a Lammermuir Festival ends with a sell-out concert in St. Mary’s Parish Church, Haddington. And if year three is sufficiently far along the line to break with tradition, then this year’s surprise was not box-office focused but based on choice of repertoire; not a Bach/Handel finish, but an all-French programme.

Ibert’s 1956 Hommage à Mozart is one of the best openers I have heard in a long time. His last orchestral work, this neo-classical romp of a rondo was written to celebrate the 200th anniversary of Mozart’s birth and, in the hands of Northern Sinfonia, it was a rousing experience. The joyously returning theme is offset by some gripping contrapuntal passages. The brass and wind were excellent in the second of these.

When a new instrument achieves conservatory status there is the small problem of available repertoire. Pleyel’s new pedal-free, chromatic harp occasioned such a need and Debussy’s commissioning resulted in Danses sacrée et profane. There are typical Debussy trademarks such as parallel and whole-tone harmony, and some lovely lush string writing as the work emerges from faux-ecclesiastical modality into more coquettish profanity. The soloist, the excellent Sharron Griffiths, has been very impressive in this festival.

Northern Sinfonia’s beautiful string sound came to the fore in Fauré’s suite Pelléas et Mélisande. Also very impressive here was orchestral ensemble. Directed unfussily from the violin by Bradley Creswick, the orchestra’s balance and phrasing were outstanding. The Prélude featured some lovely, sensitive solo moments in the wind; clarinettist Jann Ghiro’s tone and phrasing were particularly beautiful. Juliette Bausor’s flute playing shone in the elegantly played Sicilienne. This soaring melody over, she was immediately required to “head south” in search of the very atmospheric low notes which herald Mélisande’s demise. It was a real treat to hear the music of this underrated innovator of harmony and orchestration played by such an excellent ensemble in this rewarding acoustic.

After the interval Northern Sinfonia were joined by the 122-strong National Youth Choir of Scotland (NYCOS) for Fauré’s Requiem. Fauré seemed to regard his remit as offering comfort; dread inducing “dies irae” speculations are kept to a hair-raising minimum. Perhaps this accounts for the work’s abiding popularity.

Conducted by Christopher Bell, who founded NYCOS in 1996, the choir’s attention to detail belied their youth. I had the distinct impression that scores were held merely for prompting, as their gaze seemed to be directed at Bell and the audience. As a result, phrasing, diction and projection were all extremely impressive. Thanks to excellent choral balance, lines emerged which had I had never registered before, such as the heroic tenor line at “quia pius es” (“because you are merciful”) in the Agnus Dei. The choir were also capable of transparently gentle sounds such as the Amen which closes the Offertoire.

Due to Fauré’s adventurous harmony, there exist many passages which would test most choirs. The Offertoire contains several such moments where the audio equivalent of subsidence seems to be taking place. Such are the aural skills and pitching of this young choir that we were able to enjoy the thrilling insecurity, safe in their hands.

In the spirit of fostering youthful talent, the solo baritone role was shared by two fine young singers. Paul Grant delivered a very mature account of the Offertoire’s “Hostias” section. Donald Feist seemed very much to be enjoying one of sacred music’s most enjoyable melodies in “Libera me”. Soprano Catriona Hewitson’s “Pie Jesu” petitioned very affectively on behalf of the departed for eternal rest.

With such a lot of youthful talent in view it could have been very easy to take the orchestra for granted; the choral forces towered behind them; the soloists in front. Who better to gain our attention than the excellent horn section in the climax of the Sanctus? What a fantastic sound!

In a summer when the phrase “inspire a generation” has been common currency, I can’t think of a more moving example than the coupling of vocal youth and orchestral experience occasioned by this memorable performance.