'I wanted a juke box that plays nothing but flip-sides' - Jeremy Sams on The Enchanted Island

I have many files, in bulging boxes and dusty corners of my computer, of projects that, for whatever reason, never came to fruition. To be honest I’ve forgotten most of them. And I wrongly assumed that The Enchanted Island would be one of those abandoned orphans. On the face of it the notion was fanciful.

To make a complete opera out of a century of baroque music, with a new story and a new text in English. A Pasticcio, a shepherd’s pie of many ingredients, of the sort that Handel and Gluck organised in London in the 18th century. Or a Capriccio, redolent of those Italian oils of existing buildings newly juxtaposed. A folly, I thought - but that was before I reckoned with the astonishing force and focus of Peter Gelb of the Met in New York, the ‘onlie begetter’ of this piece. A man who, once he has locked on, makes things happen.

So I blithely set to work, still suspecting that this Pasticcio was probably pie in the sky. Firstly I listened. And listened. To all Handel’s operas and oratorios, followed by those of Vivaldi and other Italians (Albinoni, Marcello) then Rameau, Lully, Leclair, then Purcell and Arne and many others. It was quite a year. My rule was that anything that leapt out and demanded to be heard went on my very long shortlist. And I discovered wonder after wonder.

Then I needed a story. Since I had decided to showcase obscure music (no "Ombra mai fu"s, or "Lascia ch’io pianga"s, thank you very much – I wanted a juke box that plays nothing but flip-sides) it occurred to me that a familiar tale would make a good backdrop for the unfamiliar. Baroque composers used mythology and legend for just such a purpose. So my first thought was Shakespeare. And my second, The Tempest – an island full of magic, where people can arrive randomly.  Voice types occurred straight away. The Magus Prospero should be a counter-tenor (I was thinking of Tippett and Britten, of course), Ariel a stratospheric soprano, Caliban a subterranean bass, Miranda a lyric treble. Then I ran out of parts. Of course someone had been here before me. Dryden had done a rewrite of The Tempest subtitled "The Enchanted Island" (thanks, John, for that) to which he had added more women, on the Restoration principle that you can never have too much female flesh. Among others Dorinda, Miranda’s boy-mad sister, and Sycorax, the sorceress named but not shown by Shakespeare. I happily snaffled the latter – sorceresses are very much the stuff of 18th century opera.

This was all very well for a play, but a baroque opera is something else - an aria-making machine, and it’s love that turns the crankshaft. So I needed love interest. I thought immediately of the SATB set up of Cosi fan Tutte which led me, via Britten, to A Midsummer Night’s Dream where you find four lovers who have some previous when it comes to partner-swapping. So a mixed grill became a mash-up. The Dream lovers could be on their honeymoons, and get caught up in The Tempest, and be subject once again (with Miranda and Caliban) to a complex hockey game of amorous intertwinings, with Ariel as their Puck. Love songs, songs of loss and lust and jealousy would abound. It was maybe going to work.

Then casting began. This being the Met, the A-team were approached. Danielle de Niesse as Ariel, David Daniels as Prospero, Joyce DiDonato as Sycorax. Opera royalty. Then the message came that Domingo wanted to be part of it. Which is like hearing that De Niro wants to be in your movie - you jolly well write him a part. And actually Placido’s arrival was timely. My plot was painting itself into several corners at once, so I needed a God to turn up and sort everything out. So Domingo became Neptune. He was thrilled. He’d never played a god before.

This process, I should stress, spanned several years. Invaluable collaborators were Paul Cremo, the best dramaturge I have ever worked with, (who encouraged me, inter alia, to borrow the structure of a Broadway musical),  Phelim McDermott director and wizard, and conductor William Christie. The latter was an amazing resource. As the jigsaw took shape I found I needed specific pieces to complete the picture - so I’d ask Bill, ‘Where can I find some magic sleep music?’ (Vivaldi’s Tito Manlio)  or, ‘Do you know any angry trios?’ (Yes, from Handel’s amazing Susanna) .

Whenever I faltered in the making of this piece, which was frequently, kind souls would say, "Come on Jeremy, if you can’t do this, no one can". At the time I only believed those last three words. But, now in retrospect it seems an appropriate endeavour for me, a musician and linguist who wandered into theatre (and thence opera) and found a place where I felt I that my particular knacks made a bit more sense, and might actually be useful. The theatre is good for that. It’s where the odd bods meet up and feel a bit less odd.

Nowadays I find the same sense of making sense when teaching. And it is therefore thrilling that my Pasticcio is now being tucked into by young and hungry talent, who are using it to learn from and to train with, as much as to enjoy. British Youth Opera are a great thing (made out of three great words) and I am delighted that they are giving The Enchanted Island its first European outing.

It should be fun.

• British Youth Opera's The Enchanted Island in tandem with The Rake's Progress at the Peacock Theatre from 1 to 8 September
• Opera reviews on theartsdesk