This morning I was listening to Nick Mason of Pink Floyd being interviwed on the radio here in the UK.
It seems that Grapelli and Yehudi Menuhin were recording in the next studio when the Floyd were putting down 'Shine on You Crazy Diamond'. When he was finished in his own studio Grapelli came in and sat in on one of the Floyd's takes. They're going to release it some time next year.
SP