It is seven years since Peter Leech upped sticks and left Oxford for pastures new, having made his mark as conductor of the City of Oxford Choir and the Cathedral Singers of Christ Church. Since then, he has become an honorary research fellow at Swansea University, where he can indulge his passion for 17th- and 18th-century music, while his edition of a newly-discovered manuscript by Jesuit composer Antoine Selosse was published in 2008 and recorded on the Deux Elles label two years later.

Now he is back on his former stomping ground with vocal ensemble Harmonia Sacra, which he founded in 2009 to perform music of the late Renaissance and early Baroque periods. The choir makes its Oxford debut tomorrow night, in the glorious setting of Christ Church Cathedral.

“It’s good to be back,” he says. “I’m still very much in touch with contacts I made at Christ Church — it’s great, because they make an effort to follow what I’m doing. It’s a funny place, Oxford . . . it does have a magnetism, and the venues are so fantastic.”

So what inspired him to start this new choir? “Over the years, a lot of people I’ve worked with have said they wanted to sing in a small group to be a specialised ensemble. My main area is early music, and you can do that much more successfully with small groups. So in 2009 I invited everyone together and they made a fantastic sound, so we thought we’d take it further.

“We do all sorts of things, mainly early music, but we’ve also been commissioning work from young composers. We’ve struck up a rapport with Lawrence Whitehead, who’s written us a couple of superb pieces.”

Harmonia Sacra is based in the South West, but its members come from as far afield as Manchester, and gather every so often for weekends of intensive rehearsal.

“It’s mainly amateur singers that I’ve worked with over the past few years, and they just gelled,” says Peter. “They all sing in various other groups, but they’ve all worked with me.”

The repertoire for tomorrow night’s concert is drawn largely from the choir’s debut CD Cherubim and Seraphim, which was recorded at the Church of St Thomas the Martyr in Bristol in July 2011, and released on the Nimbus label earlier this year. The CD focuses on Russian Orthodox composers from the courts of Catherine the Great through to Nicholas II, and some of the tracks were featured in a BBC3 radio documentary last October. The repertoire was inspired by Peter’s fascination with the fusion of different musical cultures.

“I’ve always been interested in composers uprooting themselves and landing in another country, and you hear this wonderful fusion,” he says. “So you’ve got a Slavonic text with these grand, baroque fugues. “In the concert we’ll be doing a few pieces from the CD, but also some composers from mid-18th century Rome, whom the Russians tried to emulate. The disc chases the history of the style from the mid-18th century to Rachmaninov, but the concert will focus more on the 18th century.”