Singing is the act of producing musical sounds with the voice, and augments regular speech by the use of both tonality and rhythm. One who sings is called a singer or vocalist. Singers perform music known as songs that can be sung either with or without accompaniment by musical instruments. Singing is often done in a group of other musicians, such as in a choir of singers with different voice ranges, or in an ensemble with instrumentalists, such as a rock group or baroque ensemble. As in many respects human song is a form of sustained speech, nearly anyone able to speak can also sing. Singing can be formal or informal, arranged or improvised. It may be done for pleasure, comfort, ritual, education, or profit. Excellence in singing requires time, dedication, instruction, and regular practice. Professional singers usually build their careers around one specific musical genre, such as classical or rock. They typically take voice training provided by voice teachers or vocal coaches throughout their careers.

John Mellencamp,(born October 7, 1951) is an American rock singer-songwriter, musician, painter and occasional actor known for his catchy, populist brand of heartland rock which emphasizes traditional instrumentation. He has sold over 40 million albums worldwide and has amassed 22 Top 40 hits in the United States. In addition, he holds the record for the most tracks by a solo artist to hit number-one on the Hot Mainstream Rock Tracks chart, with seven, and has been nominated for 13 Grammy Awards, winning one. His latest album, No Better Than This, was released on August 17, 2010 to widespread critical acclaim.

Mellencamp is also one of the founding members of Farm Aid, an organization that began in 1985 with a concert in Champaign, Illinois to raise awareness about the loss of family farms and to raise funds to keep farm families on their land. The Farm Aid concerts have remained an annual event over the past 26 years, and as of 2012 the organization has raised over $39 million to promote a strong and resilient family farm system of agriculture.

Amethyst Amelia Kelly (born June 7, 1990), better known by her stage name Iggy Azalea is an Australian hip hop recording artist signed to Grand Hustle Records. She is perhaps better known for her promotional songs "Two Times", "Pu$$y" and "My World" whose music videos went viral on YouTube. On 27 September 2011, Azalea released her first project, a mixtape titled Ignorant Art, saying she made it "with the intent to make people question and redefine old ideals".

Iggy Azalea was born Amethyst Amelia Kelly in Sydney, Australia but moved with her family to Mullumbimby when she was still a baby, into a house on 12 acres that her father built by hand from mudbricks in New South Wales. Her father was a comic artist and painter and her mother a real estate agent. Azalea says her father "made her look at [art] as a teenager" which has always influenced her life and work.

Azalea began rapping at age 14. Azalea took her stage name from her family's dog while growing up. Before embarking on a solo career, Azalea formed a group with two other girls from her neighborhood: "I was like, I could be the rapper. This could be like TLC. I’ll be Left Eye." Azalea eventually decided to leave the group because the other girls weren’t taking it seriously: "I take everything I do serious. I’m too competitive."

Oprah Winfrey (born Orpah Gail Winfrey; January 29, 1954) is an American media proprietor, talk show host, actress, producer, and philanthropist. Winfrey is best known for her self-titled, multi-award-winning talk show, which has become the highest-rated program of its kind in history and was nationally syndicated from 1986 to 2011. She has been ranked the richest African-American of the 20th century, the greatest black philanthropist in American history, and was for a time the world's only black billionaire. She is also, according to some assessments, the most influential woman in the world.

Winfrey was born into poverty in rural Mississippi to a teenage single mother and later raised in an inner-city Milwaukee neighborhood. She experienced considerable hardship during her childhood, claiming to be raped at age nine and becoming pregnant at 14; her son died in infancy. Sent to live with the man she calls her father, a barber in Tennessee, Winfrey landed a job in radio while still in high school and began co-anchoring the local evening news at the age of 19. Her emotional ad-lib delivery eventually got her transferred to the daytime-talk-show arena, and after boosting a third-rated local Chicago talk show to first place, she launched her own production company and became internationally syndicated.

Stefani Joanne Angelina Germanotta (/ˈstɛfəniː dʒʌrməˈnɑːtə/ STE-fə-nee jurr-mə-NAH-tə; born March 28, 1986), known by her stage name Lady Gaga, is an American singer and songwriter. Born and raised in New York City, she primarily studied at the Convent of the Sacred Heart and briefly attended New York University's Tisch School of the Arts before withdrawing to focus on her musical career. She began performing in the rock music scene of Manhattan's Lower East Side, and was signed with Streamline Records by the end of 2007. During her employment as a songwriter for the record company, her vocal abilities captured the attention of recording artist Akon, who signed her to his label Kon Live Distribution.

Lady Gaga came to prominence as a recording artist following the release of her debut album The Fame (2008), which was a critical and commercial success that topped charts around the world and included the international number-one singles "Just Dance" and "Poker Face". After embarking on the The Fame Ball Tour, she followed the album with The Fame Monster (2009), which spawned the worldwide hit singles "Bad Romance", "Telephone" and "Alejandro". The album's success allowed her to embark on the eighteen-month long Monster Ball Tour, which later became one of the highest-grossing concert tours of all time. Her most recent album Born This Way (2011) topped the charts of most major markets and generated more international chart-topping singles, including "Born This Way", "Judas" and "The Edge of Glory". Besides her musical career, she involves herself with humanitarian causes and LGBT activism.