John Jensen received his musical education in Los Angeles, where he attended Occidental College and the University of Southern California, studying with John Crown, Gwendolyn Koldofsky, Ingolf Dahl and Halsey Stevens. After graduating, he freelanced around Los Angeles, and became an accompanist on several US tours for Columbia Artists Management. He later became the pianist for the Mirecourt Trio and was seen in a number of venues in Southern California.
The Mirecourt Trio subsequently became artists-in-residence at Grinnell College, commissioning upward of 30 works and recording several albums for the Music & Arts label. The trio also toured Europe twice and, through the efforts of Paul Reale, China, for a three week, three city tour where they held masterclasses and gave concerts. In 1990, Jensen left Grinnell for the Twin Cities (Minneapolis-St. Paul) where he worked with the Minnesota Orchestra and the Saint Paul Chamber Orchestra, and was collaborative pianist at St. Olaf College. He held the position of director of music at the First Universalist Church of Minneapolis for 22 years.
Jensen is in demand as a chamber music partner for many musicians in the area. He currently teaches at the University of St. Thomas, including students interested in jazz improvisation. The music of Paul Reale has been a constant in his pianistic life, and Jensen has recorded solo piano music of Reale on the Music & Arts label.