What happened in the 12th century that made the tritone possible?

Polyphony began and musical rules changed

The tritone is argued  as a musical interval composed of three adjacent whole tones. It is often defined as an interval spanning six semitones. it led to the disregard of traditional tonality.

‘yo mama attracted those indians.’ -mircromexsus

Idon’t know this answer but you can ask google i bet the answer is on there