During the 1970s Vladimir Horowitz, once described with swashbuckling hyperbole as the 'greatest pianist living, dead and still unborn' (Neville Cardus) refused all interviews whether in his adopted America or elsewhere. And so I was astonished to receive a phone call from Harold Shaw, Horowitz's suave and mega-wealthy agent asking if I would be free to come to New York to talk to his star pianist. Apparently Harold had read a review – one of qualified enthusiasm – I had written about one of his artists and decided I would be a suitable person to persuade Horowitz to play once more in Europe, something he had not done for many years. Frightened of flying and wary of anywhere outside his settled environment Horowitz was adamant.

Arriving at the Horowitz household breathless but on time (my watch had stopped) and fortunately wearing a tie (Wanda Horowitz, the pianist's wife and the daughter of Toscanini, harassed and formidable, had been known to turn those away who had the temerity to arrive late or who were unsuitably clothed, addressing them in no uncertain manner with 'you insult my husband'.) I was filled with trepidation not because of the pianist – who when caught in the right mood could be affable, sweetness and light itself – but filled with awe at the thought of his actual playing. True to form his appearance was disarming, all smiles and with his signature brightly-coloured floppy bow tie. He exclaimed in wonder over the length of my journey from London but catching his agent's eye, I explained that it was remarkably short, that the time literally flew by, and received a thumbs up sign from Harold standing discreetly behind Horowitz. A good start, then, to tempt a pianist who had become restless, tired of hearing about 'other' pianists and who wished to be considered an 'international' rather than a 'national treasure'.

Our talk (the first of three in both London and New York) ranged widely and I quickly learnt to respond to a bewildering mix of guile and naïvety. To be told that Chopin was a passionate composer was hardly revealing, but how intriguing to hear about a distant memory of playing Ravel's Jeux d'eau in Paris. An oddly insignificant little man had approached backstage and said, 'you play very well but here in France we take a less Lisztian view of music.' Horowitz was greatly amused until someone whispered, 'that was Maurice Ravel.' Disappointing, too, to be told that he had abandoned the same composer's Gaspard de la nuit ('I find it démodé') in favour of the Sonatine, music of a lesser if enchanting magic. I asked whether he played any Spanish music, my eye on the incomparable tapestry of Albéniz's Iberia only to be told, 'I'm a Russian gypsy not a Spanish one.'

Later he asked me whether I was aware of the difference between technique and mechanics, adding 'I can make many different colours. I have a good technique. Do you think I have a good technique?' I looked up sensing something teasing in such an extraordinary question, but no, only a wide-eyed quiet seeking of approval. His newly learnt work for his forthcoming Carnegie Hall recital was Scriabin's Fifth Sonata which prompted me to say that people viewed his playing as devilish, like the release of a coiled spring or, as another writer put it, like the discharge of a thousand volts of electricity. 'Ah' he responded, 'but I can play like an angel'. Later at his recital he turned to his agent and said 'Morrison says I play like the devil, so now I will show them.' Even more startlingly Horowitz asked me whether I would like him to play for me, 'something by Medtner, a Fairy Tale and part of the massive Night Wind Sonata. I haven't played any of this for years but we'll see how it goes.' To say it 'went' would be the understatement of the century. I have rarely heard anything so storming and multifaceted in my life. 'We have whole evenings of Fauré, for example, in this house, but the agents frown on non-commercial music, so most of it stays in this room,' exclaimed Mrs Horowitz.

I finally left elated, indeed, walking on air, if also bemused. I had looked in vain for part of a celebrated art collection including original paintings by Degas and Picasso. 'I had to sell them, I haven't played in public for a long time, and someone has to pay for the groceries.'

There were mischievous side-long references to other pianists, to Rubinstein ('why does he keep playing when he is so old, I hope I can still walk when I am his age. Incidentally, once I started playing again he stopped coming to see me') to Alexis Weissenberg ('he thinks he sounds like me, but he doesn't').He asked why so many young pianists were so ignorant, particularly of the art of great singers ('I never played a single piece by Brahms without knowing all his Lieder').

I was struck at every point by the outward discrepancy between Horowitz the man and Horowitz the pianist. Can there have ever been a greater contrast between a gentle whimsical nature and a pianism that had for so long had the music world by the ears? Naturally such a great pianist invites a mix of adulation and a storm of critical grapeshot, much of it marked by 'the green-eyed monster'. 'His Chopin is like a fire-ball exploding' (Rudolf Serkin); 'If people knew what Horowitz's tone meant he'd be banned from the keyboard' (William Kapell), countered by 'he is a great pianist, but I am the finer musician' together with scorn masked as sympathy, 'poor Horowitz, he turns himself inside out with his Carmen Fantasie and a woman in the audience shouts, "and now a little bit of Tosca if you please".'  'A master of musical distortion' (waspish Virgil Thomson), 'a dazzling figure-skater rather than a pianist intent on deeper values' (Ashkenazy), and more recently, 'a hollow genius' (the Guardian's Andrew Clements). Incomparable in the Russian Romantics but often tricksy and flaunting in the Viennese classics Horowtiz was also a formidable partner to Fischer-Dieskau in Schumann's Dichterliebe, too formidable for the great singer's comfort, who later took exception when he felt his own superb efforts had been partially eclipsed.

No pianist has invited greater controversy. Incandescent, a unique voice and an artist who flew heart-stoppingly close to the sun, he has in a vital sense never been equalled. It remains one of my rarest privileges to have met Horowitz, to have been given a private recital before attempting to winkle out something of his elusive genius.