When listing the attributes of contemporary classical musicians, I don’t imagine that “good sense of humour” is the first item that springs to your mind. Unless, that is, you’re thinking of HK Gruber (“Nali” to his friends), who joined trumpeter Håkan Hardenberger in an hour’s lunchtime Prom at Cadogan Hall that Hardenberger (the concert's curator) described as intended to have “a busking feel, the feeling of a street corner”.

Håkan Hardenberger © Marco Borggreve
Håkan Hardenberger
© Marco Borggreve
When Gruber sang three numbers from Kurt Weill and Bertolt Brecht’s The Threepenny Opera, it exuded from every pore that he finds Brecht’s catalogue of crooks, murderers and bent policemen utterly hilarious: he delivered the lines with a grand sweep, broad grins and knowing relish. I’ve known the work for decades and feel much the same – I’m still knocked for six every time by the intoxicating mix of Brecht’s biting sarcasm and Weill’s catchy, inventive, contagious music – but it was quite obvious that Gruber was infecting everyone in the audience, not just the hardened Dreigroschenoper fans. Never has the grand intonation of Peachum in his “morning chorale” been delivered with more wit and irony (that the miserable sinner should fulfil his destiny by getting on with it and sinning some more – i.e. by stealing for Peachum). Next was the Cannon Song, in which the murderer Macheath and Tiger Brown, the corrupt chief of police and Macheath's old drinking buddy, recall their days in the colonial army making mincemeat out of the darkies: Gruber and Hardenberger sang the pair with unabashed joy, interleaved with Hardenberger giving us Weill’s superb trumpet part.

In similarly sarcastic vein, the Song of the Inadequacy of Human Endeavour followed (more awesome trumpet playing from Hardenberger and the cheekiest vocal yet from Gruber) after which came a helter-skelter dash through the Mandalay Song from Happy End. Then it was time for lighter fare: Weill’s Song of the Rhineland, a drinking song to words by Ira Gershwin with a cascade of groan-inducing rhymes, duly delivered with gusto. Who else, other than possibly Noel Coward, would have rhymed “the girls is juicier” with “the goosestep goosier”?

A nod to the accompanists: Mats Bergström on guitar/banjo and Claudia Buder on accordion lent the perfect degree of understated swing to proceedings,ably supported by pianist Helen Crayford.

Surrounding the vocal hilarity was a varied set of instrumental pieces. I was blown away by Hardenberger’s playing of Roland Pöntinen's arrangement of The Seagull, by Swedish jazzman Jan Lundgren. Since hearing him for the first time, I’ve always felt that Hardenberger could have been one of the jazz greats had he chosen to go that way, and the gentle, slightly schmaltzy lilt of his flugelhorn was utterly bewitching. Sputnik, by fellow Swede Tobias Bröstrom, which opened the concert, fared less well: Hardenberger’s piccolo trumpet was fun, but I didn’t quite get the sense of togetherness with the orchestra.

I won’t list every number in a highly eclectic collection, except to say that Gruber conducted a set of three of his own pieces from back in the 1960s – no words this time, but still music which sparkled with humour.

Gruber’s Busking gets its London première at the Albert Hall on Wednesday, with the help of Hardenberger, Bergström and Buder. If they ever do decide to actually go and busk on a street corner somewhere, I hope they call me first, in good time. It’ll be worth the flight.