Walter Meyer asks of Norwegian composer Geirr Tveitt:

>I knew nothing about this composer until reading this post and, checking
>him out in the New Grove, discovered nothing about the way so much of his
>music was destroyed to which you allude.  Could you tell us more?

Tveitt was an inveterate tinkerer of his music, so much so that he would
come in with revisions of music between final rehearsal and performance.
For this reason, he was very reluctant to publish his scores.  Indeed, as
a performer, he almost never played anything of his the same way twice.
His own recordings are not necessarily a reliable guide to his final
wishes.

As a result he kept his scores in his wooden house.  The house burned down,
roughly ten years before his death, and the scores went with it.
Apparently, over 300 works were lost.

Steve Schwartz