Roland Petit died this morning aged 87, a world choreographer of chic and erotic theatricality who blew away the French classical ideal in a roar of post-war sexual liberation. He created an all-male corps of swans for Swan Lake long before Matthew Bourne, and his roles for his exquisite wife, Zizi Jeanmaire, repositioned ballet drama upon the femme fatale rather than the virgin. Arguably, though, for British ballet-goers he was above all the seducer who almost lured Margot Fonteyn away to France (and who got her to have a nose job) just as she was leading the Sadler’s Wells Ballet to international glory. Had Fonteyn done so, the history of Britain’s ballet would have been different.

It’s not often that a venue’s stage door is easier to find than its main entrance, but The Old Vic Tunnels is one such location. For those behind Coming Up Later, however, this is all part of the fun of a three-evening underground festival featuring a rather wonderfully haphazard range of performances. The event is the product of The Old Vic’s outreach programme, Old Vic New Voices, and the funding and artistic crowd-sourcing network IdeasTap.com. Such collaboration resulted in an opportunity few emergent creative directors could ignore: a production team, a budget to play with and three expansive tunnels for those who could imagine how best to use them.

There are few absolutes left in contemporary theatre. Fourth walls have long since crumbled underfoot; site-specific and immersive theatre experiences have further done away with divides between theatre and world, performer and audience. The one principle you can rely on is that consciousness is generally a good thing – that a play capable of putting you to sleep is bad. Oh, and that turning up to an opening night in your pyjamas is guaranteed to get you sent straight home again. Step forward maverick theatre company Duckie and their new show Lullaby, hoping to change all that.

The two-course evening out is made possible by the Wigmore Hall’s late Friday-night concerts, so if you get out of a central-London show - or dinner - by, say, 9.30, you can add a second layer of entertainment at 10. In my case, a ferociously poor hour spent at contemporary dance in Sadler’s Wells was offset by an hour with Joanna MacGregor in a stimulating splicing of Bach and Shostakovich piano music that at least offered something to think about, if not ultimate satisfaction. Evening not entirely wasted, then.

Apocrypha is a word that has acquired a dubious meaning, for books of questioned value and authenticity, texts in various religions that may not necessarily be held divine. The Belgian-Moroccan dancemaker Sidi Larbi Cherkaoui's dance work Apocrifu applies the word and its queries to the holiest of texts themselves, the Koran, Bible, Kojiki, in a secular era where religion is more about politics than faith.

In the lager-carpeted sweat box that is the KCL student union it was hard to fault The Mummers. There are some concerts where band and audience seem so lost in a private world that you can almost forget that the humdrum, everyday world even exists. Last night was one. It was no surprise that Raissa Khan-Panni and her gang were there to transport us. What did come as a revelation, however, was just how big it sounded. The musicianship was just the half of it, though.

This weekend's classical highlights comprise an eloquent tribute to a 20th-century master, entertaining cabaret songs from Weimar-era Berlin and some sublime Bruckner choral music recorded by an Edinburgh choir.

Bear with me while, like supergroomed rising star Miloš Karadaglić retuning his guitar to a mellower vein, I adjust my concert-hall vocab and describe this as a no-gimmicks sell-out gig underground with young musicians from the London Philharmonic’s Foyle Future Firsts scheme presenting two varied sets and Karadaglić headlining. And now I’ll just revert to old habits and declare the meat to be a slice of Classicism chromatically spiced (Mozart) and a 20th-century maverick pushing Neo-Baroque into near-atonality (Stravinsky), our top guitarist serenading by way of late-night coda. All this to listen to with the intent of a seasoned concertgoer or to doze to with drink in hand, as you please.

Not that some of the sweet juve players were entirely cool with it. When you've always kept your audience at arm's length in a recital space, it can't be easy to find folk at tables right under your nose texting and quaffing. But the point is that this was good practice even for the less seasoned meeters-and-greeters, since the set-up had to include introductions varying from the read-out high-falutin programme note your average newcomer to classical cabaret just wouldn't get to a bluff line in curt preface: of the Poulenc Sonata for trumpet, trombone and horn, we were told, "One critic said that this was 18th-century music with wrong notes. They're not wrong notes, and we hope you like it."

I did, and I also liked bassoonist Laura Vincent's personable introduction to the two movements of Stravinsky's Septet, toughest numbers on the programme for which there was no avoiding a bit of explanation about a passacaglia and a gigue verging on atonality; she even got away with the "Stravinsky was the Madonna of his time" line. And James Turnbull is a natural, brimming with genuine enthusiasm for one of the best oboe pieces not actually written for oboe, as he put it: "Nightclub 1960" from Piazzolla's History of the Tango, transcribed from the flute-and-guitar original. He delivered it with panache alongside subtle harpist Elizabeth McNulty, whose earlier glissandi in the Debussy Trio had showered stardust over late, lamented Humphrey Lyttleton's stuffy but ever-atmospheric venue (reprieved, I'm delighted to hear, from imminent execution).

The "sets" were well thought out in chunks of 25 minutes each, the first sandwiching the Debussy and a movement from the Ravel duo-sonata - stunningly executed by violinist Emily Dellit and cellist Arturo Serna - between Stravinsky's trio arrangement of numbers from The Soldier's Tale, and the Poulenc, showcasing a nice line in vibrato-ed trumpet song from Ellie Lovegrove. Good to know, too, that laughing at musical humour is not the prerogative of all-too-knowing Wigmore old-timers. The slow movement from Mozart's Quintet for piano and winds was the stilling heart of the second sequence, nicely set up by a Julian Anderson miniature and bringing together seven of the 14 players (most of them pictured above) sharing the platform for the later Stravinsky. Some of the groups need to loosen up and just enjoy the freedom such a space can give them, but again, it's all good practice, and drew the listeners in even as the old air con chuntered and the bar flies chattered.

Total silence, on the other hand, greeted the star turn. Fair enough, 28-year-old Karadaglić has a new CD to flog, his first for Deutsche Grammophon. Surely conscious of the matinee-idol looks which are going to be a selling point, he accounted for himself in a manner both much slicker and at the same time seemingly less sincere than the youngsters. But he was here on the eve of his Wigmore recital to show his artistry, and if the injunction "let's rock" didn't translate into the results, we did have more than a sample of his poetic soul. I'm no doyen of the classical guitar, and the only time I've heard the colours of a full orchestra in it was a year ago, from that absolute master Paco Peña, but there were certainly the shades and freedoms of a fine artist in the Albéniz pieces and the lullaby-esque Tarrega encore he gave us.

Karadaglić makes much of his pride in the Montenegran motherland, and finds there's no place like home every time he plays Carlo Domeniconi's variations on a Turkish song, Koyunbaba. Well, it's not great music, even if the tune it reflects upon is of the essence, but this was just what we needed at coming up to 11 o'clock: a late-night meditation that had an air of the improvised about it. Which again is the highest praise, and makes me wonder if real improvisation might not be the next step for relaxed "classical" cabaret nights like this. Bravo to the glammy ladies of Limelight for setting them up and moving them forward; they'll surely run and run.

• Next Limelight event in August features soprano Danielle de Niese
• Karadaglić's next recital is at the Wigmore Hall on 15 April
  
• Further details about the LPO Foyle Future Firsts scheme

Next page: Karadaglić plays part of Albéniz's Asturias