1992, Haydn graduated from Brown University with a BA in political science and began to pursue a career in music. Her debut album, Lili, was released in the fall of 1997. Following the album's release, she toured as an opening act for Jimmy Page and Robert Plant's 1998 tour of North America. Her second album, Light Blue Sun, was released in 2003, followed by 2008's Place Between Places, which she promoted with television and radio appearances such as The Tonight Show with Jay Leno, and NPR. NPR described "Place Between Places" as "A mix of neo-psychedelic flower child and rock star virtuoso...Heifetz meet Hendrix." She contributed to the score of the Edward Burns/Jennifer Aniston film She's the One (1996), as well as several films with Hans Zimmer, including Disney's Pirates of the Caribbean: At World's End. Haydn won a fellowship to the Sundance Film Institute composing in 2009, and has composed the film scores for three films, Jacklight, The Horse Boy (premiered at Sundance Film Festival and released in 2009 by Zeitgeist Films), and "The Lightmaker". In 2008, Haydn accompanied Roger Waters at the Coachella music festival when they played "The Dark Side of the Moon". Haydn also performed on Cyndi Lauper's True Colors Tour 2008. That same year she appeared on the cable TV series, Californication. In 2009, Haydn sustained neurological damage after being exposed to the pesticide Chlordane. While she was unable to write lyrics, she was still able to compose music. For the five years, she continued working on film scores and composed music for her fourth album, Lililand, released in September 2014. Since the release of "Lilliland" in 2014, Haydn has scored seven films, including Academy Award winner Freida Mock's "Anita", "The House that Jack Built", and Sundance Selects' "Driver X." She has also worked on the score for Seasons 2 and 3 of the Emmy winning series "Transparent" and done four high-impact TED presentations. In 2018, Haydn joined with musicians Hamid Saeidi, MB Gordy, and Itai Disraeli to create the group Opium Moon. Their eponymous album was awarded a Grammy in the category of Best New Age Album. In 2021, Haydn released a new single, "Sayonara", and has been working on scoring a number of TV and film projects, including the feature documentary "Strip Down, Rise Up" by Oscar nominated director Michele Ohayon and Freida Mock's latest documentary, "RUTH: Justice Ginsburg in Her Own Words."