He later became head of the music department. Meanwhile, he taught music during the summers at USC and at the University of California, Berkeley, from 1921 to 1924, and at the University of California, Los Angeles, in 1925. By the mid-1920s he was a permanent professor at USC, teaching English, French, German, Italian and Spanish as it applied to singing. He also directed the university's glee clubs and directed choruses in addition to teaching courses in music appreciation and mentoring new teachers. In the 1930s, he collaborated on two important voice and music projects. He conducted a series of experiments with Dr. Joel Pressman at Cedars of Lebanon Hospital in Los Angeles on vocal registration. Pressman had an expertise in the larynx and developed a technique to film the larynx working. Among his findings, particularly in his collaboration with Pressman, Wagner found that vocal artists must pay close attention to refining their vibrato during performances and learn to control to increase or diminish the vibrato rate and the extent of oscillation. By exercising conscious control singers can modulate the rate if it becomes too slow or too fast, or the oscillation becomes inappropriate to the emotion of the performance. To establish that control, Wagner argued that vocalists, whether a child or adult, must pay attention to the action the musculature of the larynx that will lead to correct habits of control. Repetition and practice can lead to successful command of the vibrato. Many vocal artists, with the rise of radio and motion picture musical performances in the 1920s and 1930s, had difficulty with pitch. Wagner's study, "An Experimental Study in Control of the Vocal Vibrato," provided singers with a path to exercise control over oscillation and pitch. Wagner also conducted research with Dr. Carl E. Seashore, a prominent psychologist and educator, at the State University of Iowa where they studied the vibrato in the voice and its application to string and woodwind instruments. The focus was to remedy bad vocal vibrato. The research resulted in Seashore's book, "Studies in the Psychology of Music, Vol. 1," in which Wagner contributed the chapter "Remedial and Artistic Development of the Vibrato." When military veterans returned from overseas following World War II, they sought a university education, but were impatient with the stilted rules of teaching grammar and language. Wagner streamlined courses with his own teaching method of “Grammar Rules in Rime.” Death Wagner