As per this article: https://www.gramophone.co.uk/content/features/john-wilson-inside-the-sinfonia-of-london-s-remarkable-recording-success
The orchestra continues its acclaimed series of classic American musicals with Guys and Dolls, another labour of love. ‘We live in an era of reinvention and reimagining,’ says Wilson, ‘and I think it’s easy to lose sight of what these pieces were like when they were first performed. If I’m honest, I don’t think you can improve on them. Frederick Loewe wouldn’t let an arranger change a semiquaver of his original piano sketches. “Don’t change my harmonies!” Guys and Dolls is one of a very, very, very small handful of pieces where the book, the music and the lyrics are on an equal footing. It’s a brilliant masterpiece. The original orchestrations, restored by Larry Moore, had never been recorded complete until now, and so we recorded every single note.’
And further on: 'Then the week after that, we are recording West Side Story!’