William Walker was an American Baptist song leader, shape note "singing master," and compiler of four shape note tune books, the most notable of which was Southern Harmony. After the publication of Southern Harmony, Walker added A.S.H. (Author of Southern Harmony) after his signature.

Walker was born in Union District, South Carolina, and grew up near Spartanburg. To distinguish him from other William Walkers in Spartanburg, South Carolina, he was nicknamed Singin' Billy. He worked as a singing school teacher and a normal school music teacher, in addition to owning a bookstore in Spartanburg. Walker and his family joined the newly-formed Spartanburg Baptist Church in 1839, and served as a deacon, a frequent messenger to the association, and a leader of congregational singing.

Bailey died in Spartanburg on September 24, 1875 and is buried in Magnolia Cemetery, Spartanburg. Beginning in 1994, Wofford College has hosted an annual William Walker Memorial Singing event of shape note singing.