The English diction texts by Madeleine Marshall and Kathryn LaBouff are two ofthe most acclaimed manuals on singing in this language. Differences in style between the two have separated proponents to be primarily devoted to one or the other. An in-depth study, comparing the precepts of both authors, and applying their principles, has resulted in an understanding of their common ground, as well as the need for the more comprehensive information, included by LaBouff, on singing in the dialect of American Standard, and changes in current Received Pronunciation, for British works, and Mid-Atlantic dialect, for English language works not specifically North American or British. Chapter 1 introduces Marshall and The Singer’s Manual of English Diction, and LaBouff and Singing and Communicating in English. An overview of selected works from Opera America’s resources exemplifies the need for three dialects in standardized English training. Chapter 2 reviews notational and diction resources, and use of the International Phonetic Association’s alphabet (IPA). Chapter 3 directly compares Marshall and LaBouff’s views of the importance of the unstressed syllable, often schwa [ә] or open I [ɪ], as vital to allowing the audience to understand the flow of the sung text, and contrasts their differences regarding < r >. Chapter 4 discusses observations in applying the tenets with singers, focusing on three arias coached for this dissertation. Chapter 5 states conclusions and opportunities for further research. Figures include materials from the Juilliard School Archives. Appendices include interviews.