Thesis (Ph.D. (Applied Language and Literary Studies))--Potchefstroom University for Christian Higher Education, 2003. ; The purpose of this study is to investigate the Tonal NRG (previously known as the Tonal Action) of the Lessac Approach as a voice-building tool for the female voice in theatre. It provides an overview of existing scholarly writings on the pedagogical, physiological and acoustical qualities of the Lessac Approach. It reflects on current literature about the characteristics of good voice quality and especially the actor's formant. The empirical research on voice building in this study demonstrates that a randomised pre/post test/control group quasi-experimental design was used and is fourfold in dimension: it deals with a control group, a test group with 14 contact hours, a test group with 28 contact hours and a test group who had an extensive six-week workshop. Other variables that are reflected on are language, teacher and training methodology specificity. Investigative procedures include a questionnaire, various means of acoustic analysis and a perception panel. Where applicable, inferential statistics were done on the data. Results of the investigation are compared with existing, parallel research outputs. This study indicates very strongly that the Tonal NRG of the Lessac Approach influences the female voice positively irrespective of language, teacher and training methodology specific parameters. ; Doctoral