What made the tritone acceptable in the 12th century?

In the 12th century, the tritone began to gain acceptance largely due to the evolving understanding of harmony and Music Theory, particularly with the emergence of more complex polyphonic music. Composers and theorists started to embrace dissonance as an integral part of musical expression rather than merely a tension to be resolved. Additionally, the influence of Gregorian chant and the development of modal systems allowed for a broader interpretation of consonance and dissonance, leading to a more nuanced use of the tritone in compositions. This shift marked a significant step toward the rich harmonic language that would flourish in later periods.