A fair amount of Bruckner gets performed in Vienna, but it’s rare to hear a Bruckner Mass and even rarer to hear one programmed alongside a piece like Ligeti’s Lux Aeterna. The Viennese love these slightly outside-the-box mainstream programmes, to the extent that it’s rather puzzling as to why we don’t hear more of them, and especially given the surprising ways lesser-known hometown ensembles like the Chorus sine nomine can respond to the challenge of unfamiliar repertoire.

That this was going to be a thoroughly rehearsed concert was evident from the opening few bars of the Ligeti, which introduces its sixteen parts one by one, building up a collection of pitches crammed close together. The clusters are established for long enough that the new notes from outside this set appear at first to have a destabilizing effect – with the practical repercussion that it is a nightmare to keep this a cappella piece in tune. But the choir managed admirably with the merest handful of forgivable slips, showing that the purpose of this exercise is not to torment choral directors but rather to create a series of revealing transformations, with each new configuration coming slowly into focus like a point of light. Much can be made of the strangeness of Ligeti’s timbre (the basses must sing in falsetto), but with ethereal singing and absolute evenness this was a performance which focused more on the work’s otherworldly quality.

Morten Lauridsen’s Ubi caritas et amor was just as capably sung but I didn’t care much for the piece, which repeats the Gregorian chant over and over with increasingly hokey harmonization, and sounds like a cheap knock-off of Duruflé’s beautiful choral setting.

Bruckner’s masses, however, are masterpieces, and the second in particular looks simultaneously backwards and forwards as adeptly as the mature symphonies. What seems archaic in gesture – the plainsong, counterpoint, and antiphony – is rendered startlingly new in its development, with Bruckner subverting tonality from within (which is very different from pushing it to its limits, as Mahler arguably did), and to intriguingly ambiguous effect. One must listen to this work at least once simply to hear the protracted Amen at the end of the Credo: a massive tonal consolidation, contrapuntally organized, and yet furnished with enough ‘problem’ notes to drive an analyst spare for weeks. But the musical interest here isn’t just limited to the geeks: this bizarre summation sounds all the more magnificent for its convolutions.

Now, I wrote above that this was unfamiliar repertoire for the Chorus sine nomine, and this isn’t strictly accurate – they have sung Bruckner masses before, if not regularly. But this reading was so authoritative it sounded like core repertoire honed with all the insight of a performance tradition to be reckoned with: the character and clarity of the counterpoint, the subtlety of contrast, the sophisticated understanding of why Bruckner manipulates his musical materials as he does; for all this and much more director Johannes Hiemetsberger cannot be praised too highly.

The instrumental ensemble matched the choir’s natural Bruckner sound with glowing sonorities of their own, and in the interpolation of Bruckner’s two Aequali (short instrumental pieces peculiar to the funeral liturgy in Linz) the burnished timbre and spacious phrasing of all three trombonists came to the fore. Playing and singing which serves Bruckner as eloquently as this needs to go to disc at the earliest possible opportunity.