An American music composer his noted for his works in American TV and film industry. Simonsen, who had a penchant for music from his childhood started playing piano at a very early age. He later went to study jazz piano and music theory at the Southern Oregon University and Portland State University.

Simonsen got his first big break in the film industry with the independent film Westender in 2003. Over the years, the composer has worked in more than 15 films. Some of his notable film credits as a composer includes Lonely Hearts (2006), The Brooklyn Brothers Beat the Best (2011), The English Teacher (2012), Girl Most Likely (2012), Life of Pi (2012), Bastards (2018) and Tully (2018), a comedy-drama directed by Jason Reitman.

Apart from films, Sinomsen has also worked in the TV industry. He has been associated with several popular series' like Dollhouse (2009-10), Battleground (2012), and Life in Pieces (2015-17).