Complex sentence: This led to the belief among many interpreters and composers that texture was the most important contrast, and that tempo should be used to emphasize this contrast: fast sections were conducted faster, slower sections were conducted or played more slowly.
Split into simpler sentences: This led to the belief among many interpreters and composers that texture was the most important contrast and that tempo should be used to emphasize this contrast. Thus, fast sections were conducted faster, slower sections were conducted or played more slowly.