context: The family of instruments used, especially in orchestras, grew. A wider array of percussion instruments began to appear. Brass instruments took on larger roles, as the introduction of rotary valves made it possible for them to play a wider range of notes. The size of the orchestra (typically around 40 in the Classical era) grew to be over 100. Gustav Mahler's 1906 Symphony No. 8, for example, has been performed with over 150 instrumentalists and choirs of over 400.
question: బ్రాస్ పరికరాలు వివిధ రకాల స్వరపరికరాలను వాయించడానికి ఏది అనుమతించింది?
answers: rotary valves