As a music theorist, Theisen specializes in the analysis and pedagogy of 20th-century and contemporary classical music. He has presented research at academic conferences (Society for Music Theory, Music Theory Southeast, Music Theory Midwest, Rocky Mountain Society for Music Theory, South-Central Society for Music Theory, etc.) on the music of Elliott Carter, Gyorgy Ligeti, Pierre Boulez, and Frank Martin. He is currently writing a book analyzing the later music of Dutch composer Tristan Keuris. Theisen has served as engraver of the 8th, 9th, and 10th Editions of the best-selling textbook Music for Sight Singing by Nancy Rogers and Robert Ottman.
Read: a brief analytical essay on Elliott Carter's song "Una Colomba"
Read: What's the Big Deal about All-Interval Tetrachords and the All-Triad Hexachord?
Read: Text, Harmony, and Transformation in Frank Martin's Sechs Monologe aus Jedermann
