But what did you say to this poor pianist after the "performance"?
It was hard to know what to say or how best to say it, really. Sorabji was still alive then and I had arranged with him that I would take this pianist to him the following day to play to him - until I'd heard said pianist, that is. Sorabji would have been horrified had I proceeded with this visit and, with no small embarassment and due apology, I accordingly cancelled it at less than a day's notice.
In an effort to remain as discreet as possible, I told the pianist that his representations of this and two other Sorabji pieces were entirely at odds with the composer's intentions and that, in all conscience, I could not therefore expect to accompany him to the composer so that he could play to him. Only at this point did I discover that this pianist was already scheduled to perform some Sorabji in public and I had to explain to him that he would not be able to do so with the composer's sanction. No one but the pianist could then have cancelled this event - and it was not cancelled. Unsurprisingly, I did not attend it myself. One distinguished and knowledgeable critic who did so told me afterwards that, although he had often queued to get into concerts, this had been the first that he'd queued to get out of.
This was certainly an experience of the kind that I have no desire ever to have to repeat. My rôle and desire is naturally not to seek to stand as judge and jury over different musicians' interpretations of Sorabji - far from it - but on this occasion I had to confront not legitimate interpretative licence but complete distension and distortion of the music.
I am sorry that you've reminded me of this profoundly unpleasant occasion, but I can understand why you asked the question to which I hope you find this a satisfactory answer.
Best,
Alistair