The media have sometimes labeled her as one of the most prominent members of the modern psych folk movement. Newsom, however, claims no ties to any particular music scene. Her songwriting incorporates elements of Appalachian music and avant-garde modernism.

She was exposed to music from a young age. Her father played the guitar and her mother was a classically trained pianist who played the hammered dulcimer, the autoharp and conga drums. Newsom attended a Waldorf school where she studied theater and learned to memorize and recite long poems. This skill helps her to remember lyrics while on tour.

At the age of five, Newsom asked her parents if she could play the harp. Her parents eventually agreed to sign her up for harp lessons, but the local harp instructor did not want to take on such a young student and suggested she learn to play the piano first. Starting at the age of four she began playing the piano. Only later did she move on to the harp, which she, “loved from the first lesson onward.”

From her instructor, Joanna learned composition and improvisation. She first played on a smaller Celtic harps until her parents bought her a full-size pedal harp in the seventh grade.

After high school Newsom studied composition and creative writing at Mills College in Oakland, California. While at Mills, she played keyboards in The Pleased. She dropped out of the school in order to focus on her music.

In 2002 and 2003, Newsom recorded two EPs, Walnut Whales and Yarn and Glue. These homemade recordings were intended to serve as a document of her early work; she recorded them on a Fisher-Price tape recorder. These EPs were not intended for public distribution. At the suggestion of Noah Georgeson, her then-boyfriend and recording engineer of the EP, she burned several copies to sell at her early shows. John Fellman, co-producer of Mission Creek Music and Arts Festival, claims to be the first to have booked a show for her.

A friend of Newsom’s passed one of these CDs on to Will Oldham at a show in Nevada City. Oldham was impressed with Newsom’s music and asked her to tour with him. He also gave a copy of the CD to the owner of Drag City, his record label. Drag City signed Newsom and released her debut album The Milk-Eyed Mender in 2004. Shortly thereafter, Newsom toured with Devendra Banhart and Vetiver and made an early UK appearance at the Green Man Festival in Wales, returning to headline in 2005, 2007 and 2010.

Her second album Ys was released in November 2006. The album features orchestrations and arrangements by Van Dyke Parks, engineering from Steve Albini and mixing by Drag City label-mate Jim O’Rourke.

Newsom is known to debut songs impromptu at her concerts. On March 28, 2009, she performed over two hours of new material at a ‘secret’ concert in Big Sur, California with fellow Nevada City singer-songwriter Mariee Sioux under the pseudonym ‘The Beatles’s’. Those in attendance reported that about one-third of her new material was played primarily on piano, with a backing arrangement of banjo, violin, guitar and drums.

Since late 2006, Newsom has performed a solo harp version of the traditional Scottish song “Ca the Yowes Tae the Knowes”.

Several of the songs on The Milk-Eyed Mender have been covered by her peers. “Bridges and Balloons” was covered by The Decemberists on their 2005 EP Picaresqueties. “Sprout and the Bean” has been covered by The Moscow Coup Attempt and Sholi. “Peach, Plum, Pear” has been covered by Final Fantasy (Owen Pallett) on the 2006 EP Young Canadian Mothers, as well as by Straylight Run. M Ward has played “Sadie” at some of his live shows.