Spiritual transcendence, ghostly wailing, harmonic deconstruction, microtonal singing – not your average concert experience, admittedly, but there again the Latvian Radio Choir (LRC) is far from being your average choral group. In what was one of the most explorative and daring concerts of the season, the LRC, under the baton of the ever-sensitive Sigvards Kļava, treated us to a fascinating range of styles and vocal effects. Comprising of 24 singers, one of LRC’s goals is to push the human voice to its limits and last night I have witnessed to sounds that I thought not possible of the human voice.

No strangers to adventurous programming, the LRC chose extracts from Rachmaninov’s sublime All Night Vigil (incorrectly named Vespers, the entire service for which would conclude at dawn with Matins) for the first half, while the second half showcased Nordic and Baltic contemporary music with surreal vocal effects. This was serious, experimental music with not even a sniff of a crowd-pleaser. While admirable and frankly fascinating for those who went, it might go some way in explaining why the hall was far from full. This was such a pity as this concert proved to be one of this year’s highlights.

The LRC have won the highest praise for their recording of Rachmaninov’s All Night Vigil and so anticipation was high. Nor did they disappoint. From the opening few bars I was much impressed by the finely sculpted dynamic range; a rich, warm forte contrasting with an ethereal pianissimo. This favourable impression only grew with each passing movement as LRC delivered the text of each canticle in crystal clear diction and pinpointing the intonation with scintillating accuracy. The second movement showed how delectably balanced the voices were; the altos hovered over the drone of the tenors which then subsided as the sopranos launched forth. The basses, warm and deep, were in the background but sounding enough to be fully conscious of them always. There was a magical quality to the “Slava Otsu” (Glory be to the Father) as the music ebbed and flowed before rising on the final Alleluia, like incense, before the Almighty.

A sense of reverence and spiritual depth informed LRC’s interpretation. I got the feeling that this was less of a concert performance and more of an intimate insight into Orthodox liturgy where the sublimity of the music was a reflection of the divine and a pathway to it. There was a touching gentleness to the “Bogoroditse devo” (Rejoice O Virgin) of the sixth canticle while the Alleluia in the ninth sounded like the pealing of bells. With the magnificent close ushering in the Resurrection, we too felt as if we had been reborn after such an uplifting experience.

Lined up against the wall, the LRC opened the second half with Norwegian composer Knut Nystedt’s Immortal Bach. Taking the opening line of Bach’s chorale Komm, süsser Tod Nystedt (who died last year at the age of 99) dissolves the original harmony by adding dissonance after dissonance, suspension after suspension, before it disintegrates mysteriously and magically resolves into the next concord.

Young contemporary Latvian composer’s Eriks Eśenvalds’ Légende de la Femme Emmurée tells the ancient Albanian folk story of how three brothers must sacrifice one of their wives in order to finish the castle they are building. This featured some plaintive and highly distinctive type of yodelling. The LRC conjured up a creepy atmosphere here with one of the soprano screeching at the top of her range and the rest of the choir singing in harsh intervals of seconds and sevenths.

For me it was Swedish composer Anders Hillborg’s Muo:aa:yiy:oum that was the highlight of the concert. Here, the LRC conjured up a fascinating palette of sounds by use of overtones. The piece demands the choir to split into 16 parts and to vocalise muo:aa:yiy:oum for around twelve minutes, while at the same time singing fiendishly difficult quarter tones, whistling, hand tremolos and a host of other recherché techniques. The piece opened with a ghostly shimmering effect that did not seem of human origin before a cascade of other colours and sonorities soon took over. I heard a cacophony of what sounded like flutes, string tremolos and vibrato, even a creaky door hinges. It was one of the most extraordinary pieces I have ever heard.

Ligetti’s Lux Aeterna sounded almost normal and familiar after such a work and the LCR captured the otherworldly effects very well here. Fellow Latvian composer, Pēteris Vasks’ Zíles Zina concluded the concert. This was a very effective piece with sibilant syllables being tossed backwards and forwards. It was not short of drama as laughter, speech, growling and ghostly crying all featured.

Showing that not all is magical and mystical, the LRC sang a popular folk song as an encore.