Question: When was the American singer and musician born who was also the client of Vern Yocum?

Context paragraphs:
Mansour Seck: Mansour Seck is a blind Senegalese singer and musician born in Podor, in the north of the country.  Best known for his collaboration with lifelong friend Baaba Maal, he has also toured and released several solo albums.

Lori Black: Lori Black (born April 9, 1954), also known as Lorax, is an American musician born in Santa Monica, California.  She is the daughter of Shirley Temple and Charles Alden Black.  She played bass for Clown Alley and for the Melvins.  She has since stopped performing, and has become a photographer.

Joey Welz: Joey Welz (born 1940) is an American musician born in Baltimore, Maryland who is best known for his tenure as pianist with Bill Haley and His Comets.  He was born Joseph Welzant on March 17, 1940 to Melba, a teacher and concert pianist and Joseph, a Baltimore city police officer.  Welz started his music career with his group The Jay Rockers in the 1950s.  Welz was amongst the first group of rock and roll pianists to start using the boogie-woogie style with his left hand.  He attributes this to the lack of a bassist in his band, forcing him to play basslines using his left hand.  In interviews he has stated that it also came in handy when he joined the Comets because the notes coming from the upright bass were often inaudible due to the limits of amplification at that time.

Rusty Willoughby: Rusty Willoughby (born June 30, 1966) is an active American musician born in Staten Island and currently living in Vashon, Washington, a suburb of Seattle.  s of 2011 , he has been vocalist, songwriter and guitarist or bass guitarist for several Seattle based bands: Pure Joy (1984–1989, 1997–2004), Flop (1990–1995), Llama (2005–2008), and Cobirds Unite (2010–).  He also briefly played drums for the Fastbacks.  He also played with Kurt Bloch of the Fastbacks, Jonathan Poneman (co-founder of the record label Sub Pop), and Scott Sutherland (of Seattle bands Model Rockets and Chemistry Set) in a Cheap Trick cover band called Sick Man of Europe, and appeared in the film "Hype! ", a documentary directed about the popularity of grunge rock.

Jimmy Farrar: Jimmy Farrar (born 8 December 1950) is a singer, songwriter and musician born in La Grange, Georgia, originally lead singer for the Raw Energy band, Farrar is best known as the second lead singer for the American Southern Rock band Molly Hatchet from 1980 to 1982, and in more recent years, Gator Country.

Little Archie (singer): Archie Patrick Himons, also known as Little Archie and latterly Aashid Himons, (September 22, 1942—March 19, 2011) was an American singer and musician born in West Virginia.  He was "a musical innovator that fused traditional country blues with reggae and world music during the late 1970s" and is best known for his "blu-reggae" band Afrikan Dreamland.

Jena Kraus: Jena Kraus is an American singer/songwriter and self-taught musician born in Philadelphia, Pennsylvania.  Discovered at the age of nine by vocal coach Rita Cavell she was thrust into the world of entertainment, and influenced heavily by her hippie parents' vast record collection.  Kraus had written her first collection of songs before the age of twelve.

Roy Clark: Roy Linwood Clark (born April 15, 1933) is an American singer and musician.  He is best known for hosting "Hee Haw", a nationally televised country variety show, from 1969 to 1992.  Roy Clark has been an important and influential figure in country music, both as a performer and helping to popularize the genre.

Graham Lindsey: Graham Lindsey is an American singer, songwriter, and musician born and raised in Madison, Wisconsin.  He played in several punk bands, including Old Skull; "the world's youngest punk band", while still in high-school.  He released his first solo album in 2003.  While retaining the punk attitude and political awareness Lindsey's music had since evolved and exposed his folk and country roots, to create a mix of folk, alternative country, Americana & country noir.  He has since released two more albums, one EP and contributed to several compilations.  Four of Lindsey's songs were used in the direct-to-DVD film "Fairview St.", released in 2010.  His song "Emma Rumble" was used in the direct-to-DVD film "Dunsmore", released in 2004.  Lindsey lives in Montana and performs with his wife Tina Lindsey.

Vern Yocum: Vern Yocum (April 15, 1909 - September 13, 1991) is best known as copyist and librarian for Frank Sinatra, Nat King Cole, and Nelson Riddle.  Many of the top artists of the mid-20th century relied on Vern Yocum’s Music Service, which was walking distance from the Capitol Records Tower.  His client list included: Frankie Laine, Billy Eckstine, Ella Fitzgerald, Rosemary Clooney, Mel Tormé, Peggy Lee, Steve Lawrence & Eydie Gorme, Keely Smith, Sammy Davis Jr., Trini Lopez, Nancy Wilson, Leslie Uggams, Roy Clark, and Julie Andrews.

Supporting paragraphs: Vern Yocum Roy Clark
Answer: April 15, 1933