Simplify the following text for a Grade 8 native English-speaking person.
Original: From 1908 to 1911 he was the principal conductor of the Vienna Hofoper succeeding Gustav Mahler ; he retained the conductorship of the Vienna Philharmonic until 1927 .
Simplified: From 1908 to 1911 he was the main conductor of the Vienna Hofoper , following on from Gustav Mahler . He kept the job of conductor of the Vienna Philharmonic until 1927 .