Complex sentence: However, there were severe divergences between him and the rest of the leading committee concerning his activities in favour of a change of the legal rights of composers of instrumental music, regarding royalties from performances of their works.
Split into simpler sentences: However, there were severe divergences between him and the rest of the leading committee. They were concerning his activities in favour of a change of the legal situation of composers of instrumental music, regarding royalties from performances of their works.