Demetrios Constantine Dounis was a concert violinist, mandolinist, conductor, and physician. Above all, he was an instructor who established some of the 20th century's most groundbreaking techniques for violin performance. The great violin masters' methodology was closely studied by Dounis, both privately and in concert, including Jascha Heifetz, Fritz Kreisler, and Eugene Ysaye. In the development of his techniques, his sharp sense of intuition played an important role. The medical history of Dounis helped form the anatomical and physiological base of his technical concepts. While Dounis's instruction is sometimes considered strictly academic, he referred to his methodology as "Expressive Technique," implying that a violinist with no technical shortcomings is a violinist with inexhaustible expressive ability.