Question: That's All Right had a B-side that was a cover of the song written in 1946 by which Bluegrass legend?
Context: "Uncle Pen" is a song written and originally recorded by bluegrass legend Bill Monroe.  Besides Monroe, the song was recorded by Porter Wagoner in 1956, Goose Creek Symphony in 1971, Michael Nesmith of "The Monkees" in 1973 on his solo album "Pretty Much Your Standard Ranch Stash," and Ricky Skaggs in 1984.  "Uncle Pen" was Ricky Skaggs' ninth number one single on the country chart.  The single went to number one for one week and spent a total of thirteen weeks on the country chart.  Bill Monroe played a character named "Uncle Pen" disappointed at the citification of Ricky Skaggs in the 1985 video for "Country Boy".  The improvisational-rock band Phish has performed their cover version of Uncle Pen over 200 times in the band's 30-year career. "Blue Moon of Kentucky" is a waltz written in 1946 by bluegrass musician Bill Monroe and recorded by his band, the Blue Grass Boys.  The song has since been recorded by many artists, including Elvis Presley.  In 2003, the song was chosen to be added to the United States Library of Congress National Recording Registry. "Cope" is a song written and performed by Gigolo Aunts.  Originally available as the B-side to the independently released 1991 "Bloom" 7" single, it was released as a single in its own right in October 1992 on Fire Records and later appeared on the Gigolo Aunts' album "Flippin' Out".  In support of that album, it was released as a promo single in the US in 1994 by RCA/BMG.  The promo single includes a cover of "Winsor Dam", a 1991 recording by Big Dipper that did not receive its formal release until the 2008 compilation album, "Supercluster: The Big Dipper Anthology".  Note that while the single attributes the writing credits for "Winsor Dam" to Goffrier/Oliphant/Michener/Waleik, other sources identify the writer of the song as Big Dipper guitarist, Gary Waleik. "Lady Friend" is a song by the American rock band The Byrds, written by David Crosby and released as a single on July 13, 1967.  The single reached number 82 on the "Billboard" Hot 100 but failed to chart in the United Kingdom.  In America and Europe, the B-side of "Lady Friend" was the Chris Hillman song "Old John Robertson", but in the UK, the single's B-side was changed to "Don't Make Waves", a song written by Roger McGuinn and Hillman.  The version of "Old John Robertson" found on the B-side of "Lady Friend" is a substantially different mix from the version that would later appear on "The Notorious Byrd Brothers" album.  "Lady Friend" is notable for being the only song penned solely by David Crosby to appear on the A-side of a Byrds' single. Bruce Hornsby's ninth studio album, a collaboration with bluegrass legend Ricky Skaggs titled Ricky Skaggs & Bruce Hornsby, marks the debut release for the duo's new musical project.  The album features reworkings of Hornsby originals as bluegrass tunes, as well as a number of traditional songs and a Skaggs original composition.  Worthy of note is the cover of "Super Freak" (the Rick James song), here turned into a bluegrass version. "That's All Right" is a song written and originally performed by blues singer Arthur Crudup.  It is best known as the first single recorded and released by Elvis Presley.  Presley's version was recorded on July 5, 1954, and released on July 19, 1954 with "Blue Moon of Kentucky" as the B-side.  It is #113 on the 2010 "Rolling Stone" magazine list of the "500 Greatest Songs of All Time". "Mrs. Washington" is a song written and performed by Gigolo Aunts and the title song from their 1993 and 1994 singles.  The song also appears on the album, "Flippin' Out".  The August 1993 7" single (catalog number: SM1 or 7SM1) includes a cover of "Serious Drugs", a 1992 single by BMX Bandits later included on their 1993 album, "Life Goes On".  That 1993 single was the first in a series of five releases by various bands on Fire Records under the Spawning Monsters moniker.  The April 1994 7" single (catalog number: blaze68) and CD single (catalog number: blaze68cd) include a cover of "Ask", a 1986 single by the Smiths that later appeared on their 1987 albums, "Louder Than Bombs" (US) and "The World Won't Listen" (UK).  The 12" single includes a cover of "Can You Get to That" by Funkadelic, a song from their 1971 album, "Maggot Brain".  Both the 12" single and the CD single include a cover of "Winsor Dam", a 1991 recording by Big Dipper that did not receive its formal release until the 2008 compilation album, "".  Note that while both the 12" single and CD single attribute the writing credits for "Winsor Dam" to Goffrier/Oliphant/Michener/Wallik, other sources identify the writer of the song as Big Dipper guitarist, Gary Waleik.  The 1994 single entered the UK singles charts on April 23, 1994, spending only one week there.  The cover art of the 1994 7" single, 12" single, and CD single features Chloë Sevigny.  The photo appears to be from the same session as the photo on the cover of the Full-On Bloom EP. Mountain Angel is a song written and performed by Dolly Parton off of her 2001 album "Little Sparrow".  This song, including the other tracks from the album, was recorded at ‘"Oceanway and The Doghouse"’ in Nashville, and at ‘Schnee Studios’ in Los Angeles.Mountain angel is a bluegrass piece with elements of folk.  In order to match the success of her previous album, The Grass is Blue, Dolly used the band Nickel Creek and the backing vocals of Alison Krauss to create a new innovative bluegrass sound.  The song was performed on several occasions including Larry King: Live to promote Little Sparrow and the Live and Well Tour.  It was also written as a tribute, and dedicated, to her father who told her these wild stories in the Smokey Mountains "Save Your Heart for Me" is a song written by Gary Geld and Peter Udell.  The song was originally written for and recorded by singer Brian Hyland in 1963.  Although not released as a single in its own right, it was included as the B-side to Hyland's song, "I'm Afraid to Go Home," and later appeared on Hyland's 1994 greatest hits album. "Hollywood Romance" is a song written by Lynsey de Paul and David Jordan.  It was released as a single on Polydor Records on 20 October 1978 in a picture sleeve, almost six years to the day of the release of their last hit collaboration "Getting a Drag", and it was play-listed on BBC Radio 1.  The record label was unusual in that it was printed in silver instead of the usual Polydor red label.  In Japan, it was released I February 1979 in the same picture sleeve cover with the title in Japanese added, plus the lyrics were added to the back cover.  The song name checked a number of classic era Hollywood movies such as "King Kong", "Last Tango in Paris", "The African Queen", "Citizen Kane" and "Tarzan" and was influenced by de Paul's move to California in the late 1970s to be with the actor James Coburn.  The B-side to the "Hollywood Romance" single is a blues song that de Paul co-wrote with Coburn, entitled "Losin' The Blues For You".  Polydor hosted a party in London to celebrate the release of "Hollywood Romance" in a Hollywood style setting complete with Busby Berkeley film clips.
Answer: Bill Monroe