Vocal range is the measure of the breadth of pitches that a human voice can phonate. Although the study of vocal range has little practical application in terms of speech, it is a topic of study within linguistics, phonetics, and speech and language pathology, particularly in relation to the study of tonal languages and certain types of vocal disorders. However, the most common application of the term "vocal range" is within the context of singing, where it is used as one of the major defining characteristics for classifying singing voices into groups known as voice types.

While the broadest definition of vocal range is simply the span from the lowest to the highest note a particular voice can produce, this broad definition is often not what is meant when "vocal range" is discussed in the context of singing. Vocal pedagogists tend to define the vocal range as the total span of "musically useful" pitches that a singer can produce. This is because some of the notes a voice can produce may not be considered usable by the singer within performance for various reasons. For example, within opera all singers must project over an orchestra without the aid of a microphone. An opera singer would therefore only be able to include the notes that they are able to adequately project over an orchestra within his or her vocal range. In contrast, a pop artist could include notes that could be heard with the aid of a microphone.

Christina María Aguilera (born December 18, 1980) is an American recording artist and actress. Aguilera first appeared on national television in 1990 as a contestant on the Star Search program, and went on to star in Disney Channel's television series The Mickey Mouse Club from 1993 to 1994. Aguilera signed to RCA Records after recording "Reflection", the theme song for the animated film Mulan (1998).

In 1999, Aguilera came to prominence following her debut album Christina Aguilera, which was a commercial success spawning three number one singles on the Billboard Hot 100—"Genie in a Bottle", "What a Girl Wants", and "Come On Over Baby (All I Want Is You)." Her sophomore and her debut Latin-pop album, Mi Reflejo (2000), a Christmas third studio album, My Kind of Christmas (2000), and several collaborations followed which garnered Aguilera worldwide success, though she was displeased with her lack of input in her music and image. After parting from her management, Aguilera took creative control over her fourth studio album, Stripped (2002). The album's second single, "Beautiful", was a commercial success and helped the album's commercial performance amidst controversy over Aguilera's image. Aguilera followed up Stripped with the soul, jazz and blues inspired, Back to Basics (2006), released to positive critical acclaim. The album produced three singles "Ain't No Other Man", "Hurt" and "Candyman". Four years later Aguilera released her sixth studio album, Bionic (2010), which incorporated aspects of R&B, electropop, and synthpop and was met with mixed reviews and low sales. Aguilera's seventh studio album is set to be released in 2012.

Adam Noah Levine (born March 18, 1979) is an American singer-songwriter and musician, best known as the front man and guitarist for the pop rock band Maroon 5. He is also a coach on the American talent show The Voice.

Levine was born in Los Angeles to Fred and Patsy (née Noah) Levine. His uncle is journalist and author Timothy Noah. He has a brother, Michael, and a sister, Julia. When he was six years old, he made the winning shot of his local YMCA championship basketball game (on a team his father coached) with no time left on the clock. He has said that the incident changed his life and gave him the confidence to be successful.

Levine attended French Woods Festival of the Performing Arts Camp (Hancock, NY) with best friend Jesse Carmichael, guitar player of the band known at that time as Kara's Flowers. He graduated from Brentwood School in 1997.

Levine has Jewish ancestry on both sides of his family (his father and maternal grandfather were Jewish), and considers himself Jewish, though according to The Jewish Chronicle, who interviewed Levine, he "has rejected formal religious practice for a more generalized, spiritual way of life". He chose not to have a Bar Mitzvah as a child.

Hugh Michael Jackman (born 12 October 1968) is an Australian actor and producer who is involved in film, musical theatre, and television.

Jackman has won international recognition for his roles in major films, notably as action/superhero, period and romance characters. He is known for his role as Wolverine in the X-Men film series, as well as for his leads in Kate & Leopold, Van Helsing, The Prestige, Australia, and Real Steel. Jackman is a singer, dancer, and actor in stage musicals, and won a Tony Award for his role in The Boy from Oz.

In November 2008, Open Salon named Jackman one of the sexiest men alive. Later that same month, People magazine named Jackman "Sexiest Man Alive."

A three-time host of the Tony Awards, winning an Emmy Award for one of these appearances, Jackman also hosted the 81st Academy Awards on 22 February 2009.

Jackman was born in Sydney, New South Wales, the youngest of five children of English parents Chris Jackman and Grace Watson, and the second child to be born in Australia (he also has a younger half-sister, from his mother's re-marriage). One of his paternal great-grandfathers was Greek. His parents divorced when he was eight, and he remained with his accountant father and siblings, while his mother moved back to England. As a child, Jackman liked the outdoors, spending a lot of time at the beach and on camping trips and vacations all over Australia. He wanted to see the world: "I used to spend nights looking at atlases. I decided I wanted to be a chef on a plane. Because I'd been on a plane and there was food on board, I presumed there was a chef. I thought that would be an ideal job."

Adam Mitchel Lambert (born January 29, 1982) is an American singer-songwriter and stage actor. Born in Indianapolis but raised in San Diego, Lambert had dreamed of becoming a performer after appearing in numerous amateur productions in his childhood and adolescence. His passion overtook him when deciding to drop out of college, pursue his career, and perform in various professional theatrical productions across the world.

Lambert came to prominence following his appearance on the eighth season of American Idol. Although he was runner-up, Lambert launched a music career with the release of his debut studio album For Your Entertainment (2009) after signing with 19 in a joint venture with RCA. Debuting at number three on the Billboard 200, selling 198,000 copies in the U.S. in its first week, and reaching the top 10 in several countries worldwide, the album subsequently achieved international success with its singles "For Your Entertainment", "Whataya Want from Me" and "If I Had You". Soon after, he embarked on his first headlining worldwide concert tour, Glam Nation, making him the only American Idol contestant to do so in the year following his Idol season. The tour was followed by two live releases: an extended play entitled Acoustic Live! (2010), and a live CD/DVD Glam Nation Live (2011), which debuted at number one on the SoundScan Music Video chart. Lambert took executive producer credit and was a principal writer on his second studio album, Trespassing, which was released to critical acclaim on May 15, 2012.Trespassing made its debut in the number one spot on the Billboard 200 album chart, also topping the Billboard Digital Albums Chart and Canada's Digital Albums Chart.With this accomplishment, Lambert makes music history as the first openly gay artist to achieve the top charting position.