After a summer of operas set in what might tactfully be called fancy locations, it comes as a mild shock to return to Wales and a Don Giovanni that actually takes the composer’s instructions as its starting-point. John Caird, whose first ever production for WNO a few years back was Don Carlos, revisits Spain without a qualm. He gives us heavily embossed ironwork and carved oak, he gives us cowled monks and cloaked aristocrats.

Next week Sir John Tomlinson (b 1946), renowned mega-bass and routine frequenter of the Covent Garden stage, appears in concert at the Windsor Festival. It is a picturesque halt on a career that sees him circling the world's greatest opera houses in the most epic roles in opera. As is typical of this far from typical singer, the concert is huge in its range, encompassing Mozart, Verdi and Wagner, its lyrical portrayals ranging from servants to gods, from priests to cobblers, human conditions of every shade from ruthless to kind.

David Fray certainly has the locks to be a piano virtuoso (eat your heart out, Franzi). And he has the looks, the troubled brow, the pallor and a suitably eccentric manner (the Glenn Gould hunch and hum came out for all the runs). But does he have the hands?

When you go to a trendy London performance "space" to watch an opera about rape and murder you should probably expect a few shocks. Or, if this ain’t your first Don Giovanni, you should expect not to be surprised by whatever provocations the director may have in store – which is much the same. What you probably don’t expect is for the overture to be played electronically and/or sound like it’s been remixed by Thom Yorke. But in Robin Norton-Hale’s "new version", that’s what you get – and plenty more besides. And you know what? It really works. It does. Mostly.

Robin the boy wonder, as he was somewhat patronisingly dubbed during his prodigious rise to conducting stardom, will make a bracing Batman for Glyndebourne Festival Opera when he takes over from current music director Vladimir Jurowski in January 2014.

The history of maths and music is the history of early Greek philosophy, medieval astronomy, of the Reformation, the Enlightenment and the two World Wars. While mathematics at its purest may be an abstraction, the quest for its proofs is deeply and definingly human, charged with biological, theological and even political motive. Whether through performance or discussions about music, this year’s Cheltenham Music Festival (which begins this week) explores the mathematical processes that have both shaped and echoed the history of Western Europe and its art, tracing musical development from the polyphonic motets of the 14th and 15th centuries to the Minimalist patternings of Steve Reich.

While we are far from lacking in top early music ensembles in the UK, there’s no denying that the French have a special affinity for this repertoire. While The Academy of Ancient Music and The Orchestra of the Age of Enlightenment are virtuosic champions of the genre, if we were all stuck in a sinking hot air balloon I’d lose both before sacrificing Les Musiciens du Louvre, Les Talens Lyriques, Le Concert d'Astrée or Les Arts Florissants. So it was with anticipation that I made my way to the Barbican last night to hear the UK debut of Le Cercle de l’Harmonie, the newest French orchestra on the block.

The extraordinary Longborough Opera Festival is with us again and for the next six weeks, in Martin and Lizzie Graham’s Palladian barn theatre near Stow-on-the-Wold. This year the world’s unlikeliest Ring cycle reaches Siegfried. But the improbability doesn’t end with Wagner; there is also Verdi (Falstaff) and Mozart – also, typically, a cyclic project, which has arrived at Così fan tutte. The whole set-up is so amazing that one longs to be enthusiastic about everything. But that can sometimes be difficult.

It was Groundhog Day. Murray Perahia, due to play the Schumann Piano Concerto last night under Bernard Haitink, was indisposed and at the last minute Maria João Pires rushed in with Mozart 27. Just the same happened in 2006, strangely enough, with exactly the same three artists and orchestra. As you ponder that for a coincidence, what this shows is the powerful bonds that exist between musicians, between Haitink and these two pianists, whose virtues have much in common: impeccable lucidity and light-filled emotion.

Mozart's Idomeneo is subjected to a famous bit of abuse in Milos Forman's Amadeus. "A most tiresome piece," a courtier critic sniffs. "Too much spice. Too many notes." As it happens, not a wholly inaccurate statement. The work is quite an exotic curry of an early Classical opera.