Prior to joining the faculty in 2002, John Jantzi taught as a GTF at the University of Oregon in theory, aural skills, keyboard skills, and opera ensemble. His composition, Sing to God was a commissioned composition by the European Chapter of the American Guild of Organists in 1990. His dissertation is entitled A Post-tonal Analysis and Critical Commentary on Theordor W. Adorno's 'Vier Lieder nach Gedichten von Stefan George für Singstimme und Klavier', Op. 7.
Jantzi served as Musical Director in the United States Army Music and Theater Branch, GS-7 Music Specialist, in Wiesbaden and Mainz, Germany for seven years. He later served as Director of Protestant and Catholic Chapel Music programs with the U.S. Army Chapels in Wiesbaden and Bad Kreuznach, Germany for four additional years. While studying in Switzerland, he was choir master/organist for Emmanual Episcopal Church in Geneva, private piano instructor for the International School of Geneva, and Ballet School pianist for the Conservatoire de Musique de Genève. He continues as Director of Music Ministries/Organist at Central Presbyterian Church in Eugene since 1994.
He has performed on organ and piano and was a finalist in St. Albans International Organ Competition in England in 1983. Jantzi has conducted major works for the Eugene Chamber Singers, Central Presbyterian Church in Eugene, Oregon Opera Ensemble, Oregon Festival American Music, Chorus Master for the Eugene Opera Company and the Eugene Symphony, masterclass conductor for the Oregon Bach Festival, and musicals and operas in Germany and Switzerland.