Greater experimentation in art forms became permissible in the 1970s, with the result that more sophisticated and subtly critical work began to be produced. The regime loosened the strictures of socialist realism; thus, for instance, many protagonists of the novels of author Iurii Trifonov concerned themselves with problems of daily life rather than with building socialism. In music, although the state continued to frown on such Western phenomena as jazz and rock, it began to permit Western musical ensembles specialising in these genres to make limited appearances.