In accordance with the ideas expressed in his essays of the period 1849–51 (including the "Communication" but also "Opera and Drama" and "The Artwork of the Future"), the four parts of the "Ring" were originally conceived by Wagner to be free of the traditional operatic concepts of aria and operatic chorus. The Wagner scholar Curt von Westernhagen identified three important problems discussed in "Opera and Drama" which were particularly relevant to the "Ring" cycle: the problem of unifying verse stress with melody; the disjunctions caused by formal arias in dramatic structure, and the way in which opera music could be organised on a different basis of organic growth and modulation; and the function of musical motifs in linking elements of the plot whose connections might otherwise be inexplicit. This became known as the leitmotif technique (see below), although Wagner himself did not use this word.