Hosanna Bauer grew up as Karen Trefts in Sausalito in the 50s and 60s in an artist colony where her mother was a fabric designer and her stepfather was a drummer. Influenced musically by all the records that were brought into the house, she began singing in high school with her classmates and then later, moved to Fairfax and sang with the Tocaloma Swamp Band. She auditioned for the Fairfax Street Choir, founded and led by Marla Hunt, formerly of the Ace of Cups, in 1972 and was the lead vocalist on many of their songs. The Street Choir performed at many festivals, venues and clubs in the Bay Area from 1972-1976, including a Bill Graham show at the San Francisco Civic Auditorium with Crosby and Nash, The Whole Earth Festival in Davis, in Los Angeles at the Scottish Rites Temple with Paul Horn, and performances at Glide memorial in San Francisco.

She is featured on the Unity Records release called “Give Me Wings” singing lead vocal with the Fairfax Street Choir on “Music in the Air” by Sister Rosetta Tharpe.

She is featured on the two CDs released by the Fairfax Street Choir through Choralis Records, “Train to Glory” and “Let Your Light Guide You Home”.

The track “Will the Circle Be Unbroken” from “Train to Glory”, on which she is singing lead vocal, was featured twice as an auditory cameo in the Ken Burns PBS Documentary “Country Music” released in 2019.

Hosanna moved to Sebastopol where she performed for many years with the Love Choir, as well as singing standards with the Moonbeams. She wrote “Mermaid”, a sea shanty, to commemorate the brave work of the Bodega Bay Fire Department.