Why was this such a radical musical for its time?

The first thing audiences would have noticed was it didn't begin with a line of chorus girls doing a big rousing number. The curtain went up and there was an old lady gently churning butter, on the stage, on her own, to some sort of lightly pastoral Americana – which must have stopped people in their tracks. And this is possibly the first time ever that songs have seamlessly flowed out of dialogue, developed the narrative and developed character, continuously – and it was that integration of songs within the book of the play that made Oklahoma! a completely revolutionary piece. Although Steven Sondheim did actually point out to me that the fact that it was a huge commercial hit did no harm either, because everybody wanted to do this thing, which was, on the one hand, incredibly satisfying artistically, but also making pots of money.

So were Rodgers and Hammerstein consciously drawing on opera?

Bernstein pointed out that from the middle of the 19th century to the mid 1950s, the extreme ends, if you want to think of that way, of vaudeville and opera, were growing closer and closer together, until when you have a piece like West Side Story, every single indication in the orchestration, every staccato dot, every accent in the brass, has a dramatic implication because the entire work is so integrated. Whether Rodgers and Hammerstein were doing that consciously or not, they were certainly building on that tradition of opera and musical comedy/vaudeville growing closer and closer together with every decade that passed. And there are a few seminal signposts along the way – Showboat of 1927 being one of them – but I think it was the success of Oklahoma!, and the success of this kind of integrated musical which had at its heart operatic integration – the complete work of art – that enabled the flowering of the next decade-and-a-half where you have a string of masterpieces built on the same lines.

You’ve recorded every note of the original score.

I have tremendous respect for the piece. I think these pieces are as important to our century as Mozart’s operas were to his, and I have no qualms about saying that. And I'm only saying that because I really don't think we should undervalue these pieces – something like My Fair Lady is as perfect as The Marriage of Figaro. And so when I made this recording I was determined that we should be at least reminded of what the composer, the lyricist and the orchestrator had achieved. And we took as the text the final thoughts of Rodgers, Hammerstein and orchestrator Robert Russell Bennett. But I don't mean to say that this is any kind of museum piece because I think the recording is full of life, but we took the definitive text and that's what we’ve set down – every bit of connective tissue, the ballet, the entr’actes, the scene change music, the complete dance routines, encores, everything.

How did recording in a studio affect the performance?

This piece was designed acoustically, it wasn’t designed for microphones. You go to the theatre to interact with your fellow human beings, and the moment you have a loudspeaker in the way you lose some of the reciprocity between the stage and the audience. And so we recorded this piece as acoustically, as purely, and as simply as we could. Firstly we made a conscious decision to record it in the theatre – we put the singers on the stage, the orchestra in the raised pit in the theatre, and we had the chorus in the stalls behind me, and we captured the acoustic experience. The whole thing was cast with a very great deal of care – not just the principals but the ensemble, and the orchestra was cast with as much care as the principals, because the orchestra is the beating heart of the of the piece. And I think we’ve succeeded in giving everybody the kind of experience they would have had had they been in the front row on opening night in 1943.

You used period instruments, tell me about that.

It's no different from what any number of period instrument specialists do: finding the right kind of instruments, a deep bodied acoustic guitar, calfskin heads on the vintage drum kit from the 1940s, making sure that we play the correct doublings – I think the oboe player played four instruments, oboe, cor anglais, oboe d’amore, bass oboe – none of the kind of simplifications that were imposed upon the piece as the years went past. We've gone right back to those original colours of 1943. The late Bruce Pomahac went back to all the original sources, the original manuscript, surviving orchestral parts, different vocal scores, different original recordings, and he meticulously restored every single note of the piece, and it's been our privilege to honour his work.

What impact would you like this recording to have on the way people think about Oklahoma!?

I'd like people to see just what a really inspired masterpiece it is. A piece where every single note, every single word, earns its keep. There’s no fat on it, and I think one of the hallmarks of those qualities of this masterpiece is the fact that it sounds as fresh now in 2023 as it did 80 years ago on opening night, it leaps off the page and out of the speakers, I really feel that.

Oklahoma!, conducted by John Wilson, is released by Chandos today