She began her studies in 1940 at the Mozarteum in Salzburg, Austria.  Here, studying intensely with Maestro Vittorino Moratti, she acquired the technique that would change her life and the lives of the many students with whom she later shared it.  Maestro Moratti had learned the technique directly from Giovanni Battista Lamperti (1839-1910) at Berlin’s Königliche Hochschule für Musik.  Moratti subsequently inherited Lamperti’s studio and students after Lamperti’s death.

Prof. Thiessen worked with Maestro Moratti for almost four years before his untimely death from cancer.  Having secured his technique, she established herself as a mezzo –soprano, singing with major Orchestras and Oratorio Societies throughout Germany, Austria, Italy and Sweden.

She was invited to join the Mozarteum as a Professor of Voice, and later went on to teach at the Hannover Hochschule für Musik.  Additionally, she gave master classes for 14 summers at The American Institute of Musical Studies in Graz, Austria.  She was also invited to participate in a highly successful exchange program between Mozarteum students and students at the Oberlin Conservatory in the United States.  At one time, she had over 60 singers performing on operatic and oratorio stages around the world.

During the last years of her life, she began collaborating on a book with her protégé, tenor Edward Crader.  It was her ardent wish that the vocal technique be documented just as she had learned it from Maestro Moratti.  The book is currently in the early stages of editing, and is preliminarily titled The Art of Singing and Teaching Vocal Technique, From the Direct Line of Lamperti.

Prof. Thiessen will be missed profoundly by those who were fortunate enough to study with her and whose lives were touched and enhanced by her extraordinary talent as a teacher.  The simplicity with which she approached the music and the voice, along with her wry humor, inspired her students to the highest level of the Art of Singing.  She asked only one thing of her students:  “Do your best.”