While I'm not certain about the composer, I heard this story just
slightly different:

>  "The Italian composer Pietro Mascagni was sitting in his study one
> day when a street musician stopped outside and began to play one of
> Mascagni's pieces on his hand-cranked barrel organ.  He was turning
> the handle too quickly so that the tempo was faster than it should
> have been.  Mascagni put up with it for a few minutes, then he went
> outside, grabbed the handle, and played the piece at its proper
> tempo.  He then returned to his study.
>
>  "Next day ...

The next day the organ grinder returned and -- once again -- played the
piece at the wrong tempo.  Once again the composer rushed outside, when
he was surprised to see that the street musician was displaying a sign
in front of the organ which read, 'Pupil of the celebrated Mascagni'!"

greetings by(e) InK - Ingmar Krause