Nothing if not unpredictable, Nikolaus Harnoncourt follows his controversial reading of Porgy and Bess with three Bach cantatas, as his 80th birthday celebrations bring us full circle to a definable “alma mater” in his career. Each of these works landed on his desk in the original Das Alte Werk complete cantata series, shared with Gustav Leonhardt from 1971 to 1990, and so these live recordings represent a return to recognisable territory.

Familiarity brings its own deviations from the quixotic pioneering set, most spectacularly in Harnoncourt’s approach to Wachet auf (No 140) whose chorus is sprung doggedly, the bass-line purposeful (although intermittently dragging the tempo back) and the choir responsive to a fault. There is indeed vintage Harnoncourt to be found in the maverick instrumental voicings, the deliberate exclamation, “Steht auf” (“Rise up” – and take your lamps!), and hyperbolic phraseology in the tenor chorale “Zion hört”.

If the “live” experience brings added frisson to the glowing chambers of the Musikverein, then it occurs most tellingly in the remaining cantatas. Both duets of No 140 suffer from intonation lapses but there are no such troubles with the alternative team of soloists.

Christine Schäfer glides effortlessly through “Öffne dich” from the great Advent Cantata No 61 – Harnoncourt chooses the high pitch (B minor) as was practised in Weimar around 1714 – and Gerald Finley is worth his weight in gold for the dramatic placement of the pizzicato recitative on Revelation 3:20, “Behold, I stand at the door and knock”.

For sheer elegance and festive élan, Harnoncourt finds his home in the 1731 cantata Wir danken Gott, composed for the installation of the Leipzig town council. After all these years, Herbert Tachezi still spins a remarkable organ obbligato in the orchestral reworking of the E major Preludio from the unaccompanied violin partita, and Werner Güra and Bernarda Fink sing delectably here.

But there is one movement whose performance shines above all: Schäfer’s prayerful request for a blessing on all those who govern (in this case, the town council), “Gedenk an uns”. This is one of the most extraordinarily touching moments of Bach singing in recent years, a siciliana beautifully guided by Harnoncourt.