Walter Meyer forwarded this from a broadcast of "Schickele Mix":

>Stravinsky was present at a recording of his Septet, ...  the clarinetist
>realized to his horror that he had just been playing the wrong clarinet
>(A instead of Bb, or vice versa) throughout the movement.  He had been
>off key the entire time and hadn't noticed it.  Hurriedly he explained it
>sotto voce to the recording engineer, who hadn't noticed it either.  They
>explained to Stravinsky, who hadn't noticed the off key clarinet either
>(!), ...

My favorite experience of this sort came in a conservatory - I was walking
through the halls with an aquaintance. Upon passing one practice room she
remarked - "What awful atonal music." And it did sound like a terrible
racket for a few seconds, until I realised it was simply the worst attempt
at Rachmaninoff's second piano concerto that could possibly be imagined.

Moral: even Rachmaninoff sounds atonal if the musician does not know how
everything relates to the central cadence.

Stirling Newberry