During the rehearsals he must clarify all problems of metrics and tempi,clucidating his own pacing of the work. He must temper all dynamic markings so that the instrumental"sound" is balanced in all its components. The older composers always wrote the same dynamics vertically for each simuitaneous part,straight down the page in their scores. It was only composer-conductors like Mahler or Wagner, who realized the piualls of dynamice in cautiously marked.