First, there's the photo-call, then the signing. The queue is long and eager; necks crane as Lord Menuhin embellishes each title-page with a generous flourish. To his left, a lady in black pens a vivid ink portrait (which he later signs for her). And how right he was about those stories. One admirer recalls his first Menuhin concert, "60 years ago in Newcastle" ("It wasn't my first concert in Newcastle," Menuhin replies). Next, a frail, diminutive figure bowed with age remembers being allowed to take up the violin "as payment for looking after the chickens. I was a late starter. I was 11." Menuhin traces her slow, faltering steps, past the signing desk, through the crowds to the door. Visibly touched, he brushes his cheek, then turns to the next in the queue, radiant but grateful. "It's so very kind of you all to come and stand in line to see me."
His emotional candour is as true to the man as to the boy - certainly recalling those wonderful early records, dating from Menuhin's 12th year (the time of his sudden rise to worldwide fame). Here was a violinist who, as a lad of 15, had made famous recordings of Elgar's concerto (conducted by the composer) and solo showpieces by the great virtuosi of yesteryear. Earlier in the day I had asked him whether he still recognised that passionate, albeit youthful, exponent of Sarasate, Kreisler and Paganini. "Oh, I'm very much the same person," he replied; "only now I carry that much more intellectual baggage."
Three days before, at the Barbican Centre, he had exhibited his rostrum prowess in a vigorous performance of Beethoven's Eroica symphony with the Warsaw Sinfonia. "When it comes to Beethoven, I am a man without compromise," he says emphatically; "because the music itself knows no compromise. Other music is different - you can play with it, fashion it, but Beethoven must be carefully gauged." Menuhin senses a moral force in Beethoven's music, "although nowadays he sometimes seems out of the stream of things, which is why he is so often played with less reverence, respect and intransigence than he deserves. Beethoven doesn't so much deal with individuals as with the whole of society. He is a prophet, a painter. But prophets are often exceedingly uncomfortable. No one enjoyed being with Beethoven for too long."
Does that perhaps explain why today's audiences often seem more comfortable with Beethoven's company in short bursts, or "sound bites"? Yet there are problems inherent in "sampling" such great scores. "Take the Choral Symphony," says Menuhin - "a world, no, a universe in itself. Every note chronicles Beethoven's deepest passions, his rages, hopes and dreams - but when someone tosses off the `Ode to Joy', a theme that Beethoven took a whole symphony to bring about, I find it quite terrible! Karajan's `Euro-hymn' arrangement suggests power - `This is Europe!' it seems to say [and he beats his chest vigorously] - but it isn't meant to be a military apotheosis of victory. When I play the Euro Hymn, I play it more like a prayer."
Menuhin's consternation at persistent political and social misdemeanours runs through our conversation like an idee fixe. Comments such as "We live off each other's sicknesses" or "We are all criminals and I am a criminal... because we are producing people who have a grudge against society" shoulder in among a plethora of musical references. He believes in heredity: "After all, we can't escape it, can we? And the risk of heredity is no greater than choice by election, by appointment, or by lottery!" Yet he can also be gently self-deprecating, as when his publicist excuses the collapse of a planned joint book-signing with Lady Menuhin (the former ballerina Diana Gould, who has herself just published her own volume of autobiography, A Glimpse of Olympus) by pinpointing the danger of Yehudi's upstaging Diana. "You make me feel as if I ought to be wearing a long white robe!"
A week before his 80th birthday, Lord Menuhin (American-born, a British subject since 1985 and a member of the House of Lords since John Major put him there in 1993) is as busy as ever in his many roles as conductor, educator, musical evangelist and festival organiser. But perhaps his highest priority at the moment is teaching the young, mainly through the Menuhin School. When asked if he has revised any of his founding ideals, his reply is simple but profound: "I am protecting my world of faith, trust, beautiful music, communication and compassion against a world which so often seems to defy those values." He sees endless potential in the individual and has nurtured much talent through the School, not least the young Polish-born violinist Rafal Payne, the BBC's latest Young Musician of the Year, with whom Menuhin has just been touring in Beethoven's Triple Concerto.
Of equal interest was the appearance, at last week's London concert, of another Menuhin School pupil, pianist R Hyung-Ki Joo. Here was an extremely wilful personality, one who treated the principal cadenza in Beethoven's Fourth Piano Concerto as a fully fledged musical epic - broadly, emphatically and with a whole host of rhetorical gestures. Menuhin was obviously fascinated; but did he actually approve of Joo's interpretative freedom? He thinks for a moment. "He's a very talented pianist," he says; "I admired him. He studied with Louis Kentner [Menuhin's brother-in-law] - in fact, he's had the best musical upbringing possible. And yet when he first played for me, I noticed an unconscious effort to `say' something through the music. But that's not how it should be, this `listen to me, I'm doing something very special'. In fact, I chided him for it; I told him that Beethoven has to be pure and precise; you mustn't pull the rhythm apart, it must carry itself. The freedoms you take should be minimally dosed; you must not place yourself as the centre of attention. Some people think that wanting to express yourself, rather than the music, gives you licence to do certain things. It doesn't."
I admit that this reaction surprised me, especially considering that Menuhin hails from an age when musicians habitually took liberties with the scores they played. He has always greatly admired the German conductor Wilhelm Furtwangler (whom he repeatedly defended against accusations of Nazi collaboration) and I had expected his own Beethoven to approximate some of Furtwangler's Wagnerian aura. But, no. Menuhin actually has very firm notions about the structure of a performance. "Age has brought with it a certain... you might call it intolerance. I have definite ideas about the `freedoms' that should or shouldn't be taken. I feel a general lack of comprehension, understanding, even respect concerning the structure of Beethoven's music. Leonardo da Vinci said that unless he could draw the skeleton of a human being, he couldn't draw the flesh. He had to have the bones and proportions. Beethoven's music isn't a collage; you have to recognise the underlying rhythmic skeleton."
This concern for structural formality extends to the way music is actually presented. "There must be an element of presentation in performance," he says. "I like people who wield their bows with a flourish. I don't care for anything that's half-hearted. You must walk onto that stage as if you're looking forward to sharing something with the public. And even if you have doubts - sometimes a piece might be a little under-rehearsed - you must still try to carry it off. So there is an element of showmanship involved. But what matters is that, when you start a performance, you know how it's going to end. You don't take it note by note."
Certainly Menuhin's Eroica last week was anything but piecemeal; even the celebrated "Funeral March" was firm, decisive. "Yes - but it was also quite slow," he adds, lest un-fussiness should be misinterpreted as flippancy. The audience gave him a standing ovation before edging slowly towards the exits. But the evening wasn't yet over. As I reached the door, I suddenly heard the slow pizzicato opening of a familiar overture - Rossini's Italian Girl in Algiers. Halted in my tracks, I stood to listen. It was an astonishing performance, as spry, brilliant and colourfully inflected as the Beethoven had been uncompromising and intransigent. Lord Menuhin had again become Master Yehudi - though, this time, the orchestra did the playing.
Menuhin 80th birthday concert, with the RPO, Mstislav Rostropovich, Samuel Ramey and Anne-Sophie Mutter: Sat 7pm, Royal Albert Hall, London SW7 (0171-589 8212)