devocalize

verb3

1. •
   To make toneless; to deprive of vowel quality.

   • If we take a high vowel […] and devocalise it, we obtain a hiss […] — 1877
2. •
   To reduce the volume of the vocalizations of (an animal) by surgically removing tissue from its vocal cords.
3. •
   To remove the vocals of a song with an AI program creating a false instrumental with imperfections (vocal shadows).