After collaborating with several artists, Aguilera incorporated 1930s and 1940s blues, soul and jazz influences to her fifth album, Back to Basics (2006). The record spawned the top-ten singles "Ain't No Other Man", "Hurt", and "Candyman". However, her electronica-inspired sixth album, Bionic (2010), made little commercial impact. That year, Aguilera starred alongside Cher in the film Burlesque, and served as the executive producer of its successful soundtrack. Her seventh record, Lotus (2012), incorporated electropop, dance-pop elements and became her lowest-selling release to date. Aguilera is an original coach on The Voice, having appeared in three of its four seasons since 2011.
Aguilera has become a prominent figure in mainstream popular music and culture, and has been recognized as a pop icon, "Princess of Pop", and "Voice of Generation". She has earned numerous awards and accolades, including five Grammy Awards, one Latin Grammy Award, two Billboard Music Awards, two MTV Music Video Awards, a Golden Globe Award nomination, and a star on the Hollywood Walk of Fame. To date, Aguilera has sold over 50 million albums worldwide, with 14.5 million units certified in the United States alone. Rolling Stone ranked her 58th on their list of the 100 Greatest Singers of All Time, becoming its youngest and only artist under the age of thirty. During the 2000s, Billboard recognized her as the 20th Artist of the Decade and its second top-selling single artist, behind Madonna. Aguilera was ranked number eight in VH1's 100 Greatest Women in Music and was one of Time's 100 Most Influential People in the World in 2013. Outside of her work in the entertainment industry, Aguilera is involved in charitable activities through human rights, world issues, and her work as a UN ambassador for the World Food Programme.
Aguilera, a soprano, has been referred to as the "Voice of her Generation", a blue-eyed soul singer and one of the greatest singers of all time. She possesses a four octave vocal range and a whistle register. Aguilera also topped Cove's list of the 100 Best Pop Vocalists with a score of 50/50, and came fifth in MTV's 22 Greatest Voices in Music. Her rendition of "It's A Man's Man's Man's World" at the 2007 Grammy Awards ranked third in the Grammy's Greatest Moments List behind Celine Dion's performance of "My Heart Will Go On" and Green Day's performance of "American Idiot". In an interview, Dion described Aguilera as "probably the best vocalist in the world." Dion wrote an article on Aguilera for Time magazine's 2013 list of their 100 Most Influential People in World, saying, "The first time I heard Christina sing, I was totally blown away. Her voice has got so much power, yet so much sensitivity and technically, I think, she’s flawless." Aguilera's distinct style of singing has been praised by critics and noted as influential.
Sasha Frere-Jones of The New Yorker writes, "Aguilera doesn't need to reincarnate Sarah Vaughan to be a serious singer. She already is one, in the tradition of nineteen-nineties pop and R&B, skillfully deploying melisma for razzle-dazzle, riding the bouncy syncopation of samples with the coordination of a rapper, and timing the phrases to imply her athletic dance moves". The People's Choice Awards honored Aguilera with the People's Voice award, recognizing her vocals and "ability to reach millions of people across a number of genres including pop, soul and R&B". Rolling Stone ranked Aguilera at 58 as their 100 Greatest Singers of All Time, the youngest singer on the list.
Since her debut in 1999, Aguilera has been compared to Mariah Carey and Whitney Houston. David Browne of The New York Times writes, "Aguilera has been one of the foremost practitioners of the overpowering, Category 5 vocal style known as melisma. Ms. Carey, Ms. Houston and Ms. Aguilera, to name its three main champions, are most associated with the period from the late ’80s through the late ’90s." A review in the Los Angeles Times compared Aguilera's vocal style to Barbra Streisand, Gladys Knight, and Aretha Franklin adding, "Aguilera's Streisand-esque tendencies are a good thing; they're helping her figure out how to become the "great singer" she's been dubbed since she released her first single, the wise-beyond-its-years "Genie in a Bottle", at 18." Vocal coach Cari Cole, called Aguilera the "Queen of riffing", adding that her vocals are rooted in soul music. Although praised for her vocals, Aguilera has been labeled for oversinging in her songs and concerts. The Huffington Post named Aguilera a main proponent for "oversouling", described as the "gratuitous and confected melisma." The term was coined by producer Jerry Wexler who said, "I have found that flagrantly artificial attempts at melisma are either a substitute for real fire and passion or a cover-up for not knowing the melody." The majority of Aguilera's songs are characterized by her loud vocals, though she has used breathy and soft vocals. Aguilera co-wrote "Sing For Me" from her album Lotus, a response to critics who labeled her for oversinging. In the song, Aguilera explains why she sings the way she does, saying "I don’t even care what the world thinks about how I sound." Aguilera admits to oversinging in her early years adding, "Before, to make up for the kind of music I didn't want to be doing, I would over-riff, to prove that I have talent. It was too much". Longtime producer and writer, Linda Perry, commented on working on the track "Beautiful", saying, "I tried to keep it straight. I told her to get rid of the finger waves. Every time she'd start going into "hoo-ha", I'd stop the tape. I'm like, 'You're doing it again.'" Perry ended up using the first take saying, "She had a hard time accepting that as the final track. It's not a perfect vocal – it's very raw. She knows her voice really well, and she knows what's going on. She can hear things that nobody else would catch."