Some musicians of the period, like Marc Lavry ("Shir Ha-Emek", "Kitatenu Balayla Tzoedet"), wrote in both the new Hebrew style and the European style in which they were trained. For example, "Zemer" is a song in the new style; Dan HaShomer is an opera in the European classical tradition. Others, like Mordechai Zeira, lamented the fact that they did not write in the new Hebrew mold. Zeira, one of the most prolific and popular composers of the period ("Hayu Leylot", "Layla Layla", "Shney Shoshanim"), referred to his inability to write in the new style as "the Russian disease".