During her studies at Case Western Reserve University, Estill took 30 hours of speech and hearing elective classes, marking her introduction to voice science.

[9] From 1972–1979, Estill was appointed instructor in voice in the Department of Otolaryngology, at the Upstate Medical Center, Syracuse, New York.

[9] It was Dr. Osamu Fujimura at Ohio State University at Columbus, who assisted to gather necessary data for Jo to develop her research on her own.

[13] Estill studied various qualities associated with different styles of singing, using techniques including EMG, electroglottography, voice signal analysis, X-rays of the phonating larynx, laryngeal fibre endoscopy, acoustic measurements and simultaneous videostroboscopy.

[18] Estill is reported to have made a big impact on the theatre scene in the UK because she offered an alternative approach to the traditional way of singing training.

[19] I think that we will only understand the full effect of Jo's training model ... when we are well into the next millennium.Many authors and performers have acknowledged Estill and Estill Voice Training in the development of their own work including: Gillyanne Kayes,[20][21][22][23] Deirdre Trundle,[24] Mary McDonald Klimek,[25] Donna Soto-Morettini,[22][26] Joan Lader,[27] Lise Olson,[28] Dane Chalfin[5] and Klea Blackhurst.