"Don't expect polish," announced Ivan Fischer apologetically. "Things vill go rrrong. We may start pieces again." The tuba had been turned into a tombola. The percussionists were playing their buttocks. Someone else was blowing a Hungarian didgeridoo. A certain amount of madness was expected from the second Prom, an experimental Audience Choice concert. But the Mahler One of the first Prom? Who knew that that would be equally if not even more outrageous.

A legendary septuagenarian wind player from Switzerland returns to the repertoire with which he made his name 50 years ago, and there's an exciting live reading of a gloomy fin-de-siècle symphony conducted by a contemporary French giant. The same conductor also treats us to a sparkling Stravinsky rarity, and a youthful duo lighten the mood with some Russian fireworks on Merseyside.

The spectacle of an orchestra named after Mahler playing Stravinsky irresistibly calls to mind Stravinsky’s report of a performance of the Eighth Symphony in Zurich in 1913. “Imagine”, he wrote to Maurice Delage, “that for two hours you are made to understand that two times two makes four.” Oddly enough, repetition is the lifeblood of Stravinsky’s own music, though he rarely makes two times two equal four, and his symphonies don’t last two hours (nor, incidentally, do Mahler’s).

This year’s Choral Sundays at the Proms are a wonderfully mixed bag. Mighty choral touchstones are represented by Mendelssohn’s Elijah, both the Verdi and Mozart Requiems and Beethoven Missa solemnis, but there’s also an enticing strand of curiosities. Looming largest among these has of course been Brian’s Gothic Symphony, but emerging now from its sprawling shadow are less obscure but no less interesting works – Britten’s Spring Symphony, and last night Mahler’s folkloric Opus 1 cantata Das klagende lied.

Marley & Me: that’s the film about living with a neurotic dog, out now on DVD. And Mahler & Me? It could be the Gustavo Dudamel story. Conducting Mahler was what first brought everyone’s favourite Venezuelan to world attention, when he won the 2004 Mahler Competition in Bamberg. Given the turbo-charged excitement always stirred by his Simon Bolívar players – no Youth Orchestra now, mark you, but a Symphony Orchestra, grown-up, professional – this Prom visit would have been sold out long ago even if they were playing Glazunov.

Well, that's a first. With the final upbeat of the rustic second movement, Sir Roger Norrington Bugs Bunnied the audience. He turned to us with cheek in his eyes, a "That's-all-folks!" smile plastered on his face, brandishing his baton for a carrot, as if he and the Stuttgart Radio Symphony Orchestra had (yet again) just outwitted Elmer Fudd. The thought that Norrington's Mahler Nine would make me laugh had crossed my mind before the concert. But I had no idea that I'd be chuckling in a good way.

Everyone in the BBCSO is a potential soloist. I know this because the course I run at the City Literary Institute linked to the orchestra has welcomed principals, duos, two string quartets and three viola foursomes (proving that department the most individual, not the dense deserving butt of many a joke). I adore these players, but I love Erwin Stein's chamber arrangement of Mahler's Fourth Symphony even more, so this was bound to be a gem. Spitalfields' UK premiere of a recent song cycle by favoured Dutch composer Michel van der Aa could only come as an enterprising bonus.

There was a macabre irony at the heart of this final concert in the CBSO’s Mahler cycle in Symphony Hall. Everything was back to front. It started with a Resurrection and ended with a death. Like the universe, it began with a bang and ended, Eliot-fashion, with a whimper. And the Resurrection wasn’t even Mahler’s (that happened last month), but Messiaen’s: his Et exspecto resurrectionem mortuorum, a work which reduces redemption to sounding brass and crashing gongs.

A 20th-century Austrian symphony receives a memorable first recording, coupled with a witty, rarely played slice of Schubert. Mahler’s Resurrection Symphony is heard in a powerful reading recorded in the Royal Festival Hall. And we’ve an intelligent, logical coupling of two ballets commissioned by Diaghilev.

This week we’ve some pioneering, trailblazing Mahler with a dramatic twist, courtesy of a conductor who mentored Leonard Bernstein. Elsewhere, there are some disconcerting, dark sounds from a youthful German composer, and a supremely entertaining disc of highly theatrical vocal works courtesy of Paul Hillier’s immaculately drilled Theatre of Voices. Turn on, tune in and drop out while listening to Cathy Berberian’s cartoon-inspired Stripsody, and consider the very question of what constitutes music.