Stephen Layton knows his Bach.
The English conductor, together with Auckland Philharmonia Orchestra, delivered a memorable Mass in B minor in 2012, followed by an equally impressive St John Passion two years later.
Now he's back for the APO's enterprising Bach Collage concert which pairs Bach with the contemporary Estonian composer, Arvo Part. Working with the University of Auckland Chamber Choir is one of many drawcards for Layton.
"After all, they've been trained by Karen Grylls, who's one of the best in the world at it," he says. "With the lean, clean sound of young voices, you're off to a good start with Baroque music and especially Bach - and it fits very well with Arvo Part, too."
Talking soloists, Layton's yet to work with tenor Andrew Goodwin and bass Christopher Richardson, but describes Helen Charlston as "an alto who's really going places, with a splendid Bach voice," and soprano Sara Macliver, a regular and appreciated presence in our concert halls, as "one of the greats."
"Singing Bach, you need to be sensitive to the instruments around you," he warns. "It's not like Wagner or Puccini where the orchestra is a sound-world that the soloist floats upon. Bach asks for a marriage of instruments and voices; singers need to know instrumental lines inside out."
Thursday's concert closes with the splendour of the Magnificat which, for Layton, is Bach at his most succinct and exultant. He says its opening chorus with rippling oboes and flaring trumpets, "positively exudes joie de vivre."
The jubilant cantata, Jauchzet Gott in allen Landen (Exult in God in Every Land), launches the evening.
"Its opening aria has this marvelous combination of soprano and trumpet solo," Layton says. "Yet, after that, you have one of the most tender things Bach ever wrote, with just walking bass line and the singer suspended over it. It's almost other-worldly."
We hear Arvo Part twice on Thursday, with a 1964 instrumental work, Collage sur B-A-C-H and his 1990 Berlin Mass, a score celebrating the newly forged freedom of Eastern Europe, symbolised by the fall of the Berlin Wall. Layton sees two composers committed to writing essentially spiritual music, although Part reaches out for more than just a purely Christian audience.
The 26 years separating his two pieces, from the crunch of clustering dissonances in the Collage to the cooler minimalism of the choral work, represent a journey from darkness to light that Layton himself was able to track at Tallinn's Arvo Part Centre.
Working through the composer's papers, he saw "reams and reams of simple, single-line tunes, based on psalms.
"These weren't just the slow, white-note music that some dismiss his later style as being," he adds. "They represent a painful process - a long night of the soul - that he worked through and came out the other end."
In Auckland, the APO will use Layton's own special edition of the Berlin Mass, involving crucial modifications of bar-lines and time signatures. This met with Part's enthusiastic approval, Layton tells me, as "the last thing he wanted was for mere bar-lines to get in the way of what was being expressed emotionally."
This highly practical conductor has also ensured "orchestral musicians can see the sung text above everything they play.
"Part was particularly excited about this," he stresses. "The players can then be aware of the sympathy that the text requires. It's not always easy playing this often repetitive music but, if you can see the significance of something you're trying to shape, then you have something to hang on to."
What: Auckland Philharmonic Orchestra, Bach Collage
Where & when: Auckland Town Hall, Thursday at 8pm