Question: Who is the American musician and singer who performed a version of the traditional English folk song "The Cuckoo" and began his performance career at Southern Appalachian medicine shows?

Context paragraphs:
Six Studies in English Folk Song: Six Studies in English Folk Song is a piece of chamber music written by English composer Ralph Vaughan Williams in 1926.  It is a collection of six English folk songs set for cello and piano.  Each song follows the same format: presentation of the tune in the solo line, followed by a full iteration of the folk song in the piano with an ornamented solo line.

Cutty Wren: The Cutty Wren and its variants like The Hunting of the Wren are traditional English folk songs.  The origins and meaning of the song are disputed.  It is thought by some to represent the human sacrifice of the Year King, or the symbolic substitute slaughter of the wren as "king of the birds" at the end of the year for similar purposes, and such songs are traditionally sung on Boxing Day (26 December), just after the winter solstice.  The 26 December is sometimes called: "St. Stephen's Day" or "Wren Day".  These rituals are discussed in "The Golden Bough".  It is number 236 in the Roud Folk Song Index.

Byker Hill: "Byker Hill" is a traditional English folk song about coal miners, that has been performed by many contemporary acts.  There are at least three different tunes to which the song is sung.

Blacksmith (song): "Blacksmith" (Roud 816) is a traditional English folk song, also known as "A Blacksmith Courted Me".  The song was noted down by Ralph Vaughan Williams in 1909 from a Mrs Ellen Powell of Westhope near Weobley, Herefordshire.  On that occasion it was sung to the tune "Monk's Gate", better known as the tune of "To be a pilgrim", the hymn by John Bunyan.  The same tune is sometimes used for the song "Our Captain Cried".  There is a setting by George Butterworth (a friend of Vaughan Williams and Cecil Sharp) in his 1912 collection "Folk Songs from Sussex" (recorded by Roderick Williams and Iain Burnside in the Naxos English Song Series 8.572426).

The Unthanks: The Unthanks (until 2009, Rachel Unthank and the Winterset) are an English folk group known for their eclectic approach in combining traditional English folk, particularly Northumbrian folk music, with other musical genres.  Their debut album, "Cruel Sister", was "MOJO" magazine's Folk Album of the Year in 2005.  Of their subsequent albums, eight have received four or five-starred reviews in the British national press.  Their album, "Mount the Air", released in 2015, won in the best album category in the 2016 BBC Radio 2 Folk Awards.  In 2017 they released two albums featuring the songs and poems of Molly Drake, mother of Nick Drake.

Clarence Ashley: Clarence "Tom" Ashley (September 29, 1895 – June 2, 1967) was an American musician and singer, who played the clawhammer banjo and the guitar.  He began performing at medicine shows in the Southern Appalachian region as early as 1911, and gained initial fame during the late 1920s as both a solo recording artist and as a member of various string bands.  After his "rediscovery" during the folk revival of the 1960s, Ashley spent the last years of his life playing at folk music concerts, including appearances at Carnegie Hall in New York and at the Newport Folk Festival in Rhode Island.

The Cuckoo (song): "The Cuckoo" (Roud 413) is a traditional English folk song, also sung in the USA, Canada, Scotland and Ireland.  It has been covered by many musicians in several different styles.  An early notable recorded version was performed by Appalachian folk musician Clarence Ashley with a unique banjo tuning.

Seventeen Come Sunday: "Seventeen Come Sunday" is an English folk song (Roud 277, Laws O17) which was used in the first movement of Ralph Vaughan Williams' "English Folk Song Suite" and a choral version by Percy Grainger (1912).  The words were first published between 1838 and 1845.

The Lincolnshire Poacher: "The Lincolnshire Poacher" is a traditional English folk song associated with the county of Lincolnshire, and deals with the joys of poaching.  It is considered to be the unofficial county anthem of Lincolnshire.  It is catalogued as Roud Folk Song Index No. 299.

Billy Boy: "Billy Boy" is a traditional folk song and nursery rhyme found in the United States.  It has a Roud Folk Song Index number of 326.  It is a variant of the traditional English folk song "My Boy Billy", collected by Ralph Vaughan Williams and published by him in 1912 as number 232 in "Novello's School Songs".  The song is very popular with the Orange Order.

Supporting paragraphs: The Cuckoo (song) Clarence Ashley
Answer: Clarence Ashley