She began piano lessons with her mother, Sara, who then joined the music faculty at Valley City State University.

She also learned the trumpet and horn and performed with school bands, as well as participating in musical theater and singing with choirs.

[5] Hagen then earned a Master of Arts in Composition from the University of Minnesota, where she studied with Doug Geers and Judith Lang Zaimont, and graduated summa cum laude in 2006.

[7] Hagen has been awarded McKnight Artist Fellowships in 2010[8] and a grant from the Minnesota State Arts Board to complete a piece for the Metropolitan Symphony Orchestra in Minneapolis.

[1] She received the Live Music for Dance grant from the American Composer's Forum in 2011 and 2014 to create new works with choreographer Penelope Freeh.

In combining both sacred and secular texts, amass continues the tradition of the Catholic Mass, as well as inviting the audience to consider multiple paths to salvation.

“Frequent rhapsodic repetitions of texts throughout the oratorio allow listeners to meditate and reflect on the work’s music and its spiritual narrative without the encumbrance of new texts to consider.”[13] Hagen was commissioned by the Minnesota Chorale and the Metropolitan Symphony Orchestra to compose The Notebooks of Leonardo da Vinci, a seven-movement work for choir, orchestra, and video projections to honor Leonardo da Vinci'.

[16] The piece includes a video technician using Musaic software to adjust the film in real time to follow the conductor, and is thus a performer like any other member of the ensemble.

The Song Poet premiered in March 2023, conducted by Tiffany Chang with dance choreography by Penelope Freeh.

Hagen "approached singers interested in commissioning songs by her," and the project was supported by a collective of professional sopranos, each of which had "the right to a regional premiere of the cycle.

The ebb and flow of the sound-scape lulls the listener into deep reflection...Hagen’s music exemplifies depth as it is not only beautiful, but also inspires introspection.”[20]