One of his last compositions was the Himne a les Nacions Unides ( Hymn of the United Nations ) ; he conducted its first performance in a special concert at the United Nations on 24 October 1971 , 2 months before his 95th birthday . One of his last compositions was the `` Hymn of the United Nations '' . He conducted its first performance in a special concert at the United Nations on October 24 , 1971 , two months before his 95th birthday .