Voice training is the process of training your voice to sound a certain way. Here, this pertains to making your voice sound more masculine or feminine. While voice training is more common among trans-feminine individuals (as estrogen does not change your voice), some trans-masculine individuals who opt not to go on testosterone (or are otherwise unsatisfied by the voice drop typically provided by going on testosterone) will train their voices to sound more masculine.

Speech Voice Lab - Transfeminine Speakers
YouTube Playlist - Voice Feminization by Jordan Ross Communication
YouTube Video: Male To Female - Voice Feminization

Google Docs - Transmasc Voice Rundown Scinguistics
Speech Voice Lab - Transmasculine Speakers
Trans Guys - TESTOSTERONE AND THE TRANS MALE SINGING VOICE
YouTube Playlist - Voice Masculinization by Jordan Ross Communication
YouTube Playlist - Voice training playlist
YouTube Video: How To Achieve A Natural Male Voice

YouTube Channel: AmaRoseLessons
YouTube Channel: UndeadVoiceLab
YouTube Channel: Renée Yoxon
YouTube Channel: TransVoiceLessons