no element of expression existing in a tune of any kind, however ancient, however remote in origin, must be banished from our musical idiom. all modes, old and new, european or exotic, insofar as they are capable of serving an expressive purpose, must be admitted by us and used by composers. i believe that the polyphonic principle may be applied to all kinds of scales. our two modes, the major and minor, have been so thoroughly exploited that we should welcome all elements of expression by which the musical idiom may be rejuvenated.