BoA lists hip hop as her main musical influence, though she also enjoys R&B. Her favorite musicians are Michael Jackson, Janet Jackson, Nelly, Britney Spears, Brian McKnight, Justin Timberlake, Pink, and Jay-Z; as a result, much of BoA's music is either dance pop or R&B. Because she also sings ballads, she is often compared to fellow Japanese singers Ayumi Hamasaki and Hikaru Utada. Her debut album, ID; Peace B, contained urban pop, "slickly produced" ballads, and "upbeat dance tunes". As her career went on, she began experimenting with different styles: Valenti contained mostly ballads; Love and Honesty was an experiment with "harder" R&B and rock music.Because the composition and writing of BoA's songs is handled mostly by her staff, BoA has been criticized as being a "manufactured pop star".[note 2] In response to such criticism, BoA said that "if one person were to force their own will on something, then things that should have gone right could easily go wrong" and that she is "not all that unhappy with the expression that [she is] a manufactured star. In a way, that is true. Because SM Entertainment created the environment and all the surrounding conditions, [she is] able to be successful in the way [she is] now." Though her earlier releases were marked by a "cute" and "youthful" style, BoA began to present a more "mature" image starting from the album My Name. In a Talk Asia interview, Anjali Rao noted that some felt that My Name marked the beginning of BoA's decline in popularity and asked if the public would always see the singer as "Little Baby BoA"; BoA replied, "So while I apologize to those people who still want the baby BoA, in fact, what can I do? I just keep growing up! I can't stop that from happening." BoA has collaborated with "high-profile" artists. Among the Japanese artists she has performed with are the hip hop group M-Flo (for the single "The Love Bug"), pop singer Kumi Koda, and house DJ Mondo Grosso. She has performed with Western artists: the song "Flying Without Wings" from her album Next World was a collaboration with Irish band Westlife covering the original song; the Bratz single "Show Me What You Got" was performed with Howie D of the American band Backstreet Boys. She also worked with Akon, singing the song "Beautiful", which was featured on the Japanese release of his third album, Freedom. Other artists she has collaborated with are Soul'd Out, Dabo, Verbal (of M-Flo), Rah-D, Seamo, TVXQ, Yutaka Furakawa (of the band Doping Panda), and Crystal Kay (for her single After Love: First Boyfriend/Girlfriend). American rock band Weezer covered "Meri Kuri" on the Japanese version of their album Weezer (The Red Album).
BoA began her Japanese music career singing at the Avex-owned club Velfarre. In 2001, she released her debut Japanese single, a Japanese version of the song, "ID; Peace B" (originally from the eponymous album). The single reached #20 on the Oricon chart and was followed by "Amazing Kiss", "Kimochi wa Tsutawaru", and "Listen to My Heart"; the last became the singer's first single to enter the Oricon's Top Five. After the September 11, 2001 attacks, BoA recorded the charity single "The Meaning of Peace" with Kumi Koda as part of Avex's Song Nation project to raise funds for charity. Her debut Japanese album, Listen to My Heart, was released on March 13, 2002. The album was a breakthrough in BoA's career: it became an RIAJ-certified million-seller and debuted atop the Oricon, making it the first album by a Korean artist to reach the top. A single, "Every Heart: Minna no Kimochi", was released on the same day as the album. After the release of Listen to My Heart, BoA released her second Korean studio album, No.1, a month later. The album sold around 544,000 units and became the fourth-best-selling record of the year in South Korea. Jumping into the World (a Japanese re-release of the mini-album Don't Start Now) and the Japanese single "Don't Start Now" were released a month later on the same day.BoA's second Japanese studio album, Valenti (2003), became her best-selling album, with over 1,249,000 copies sold. In support of the album, BoA launched BoA 1st Live Tour Valenti, her first Japanese concert tour. Later that year, she released two Korean albums, Atlantis Princess and the mini-album Shine We Are!. The former was the fifth-best-selling South Korean record of the year with around 345,000 units sold; the latter sold around 58,000 units and was the fifty-second-best-selling record. Her third Japanese studio album, Love & Honesty (2004) was a musical "change in direction": it contained a rock-dance song ("Rock with You") and "harder" R&B. Though the album failed to match Valenti in sales, it topped the Oricon chart for two weeks and became RIAJ-certified triple-platinum. In support of the album, BoA held a tour, Live Concert Tour 2004: Love & Honesty. In contrast with 1st Live Tour, which "emphasized exotic Asian design", the Love & Honesty tour had an "outer-space, sci-fi" theme; among the props were a three-story-high space ship and the robot Asimo. The tour, which started in Saitama and ended in Yokohama, spanned nine performances and attracted approximately 105,000 attendants. Her first compilation album, Best of Soul (2005), however, sold over a million copies, making BoA the first non-Japanese Asian singer to have two million-selling albums in Japan. In 2006, BoA renewed her contract with SM Entertainment until 2012. At the time it was noted that she had a shareholding in SM Entertainment of 100,000 (Approximately worth 1m USD).
BoA is a "top artist" in South Korea and Japan; her popularity in the latter is attributed to her linguistic skills (she speaks and records in Japanese, Korean, and English) and a Japanese interest in Korean pop culture started in the early 2000s when the two countries began promoting cultural exchanges. BoA's popularity extends throughout East Asia; she has fans in China, Hong Kong, Taiwan, and Singapore. She has expressed plans to enter a global market; she stated in an interview, "I will [...] get recognition in the U.S. and Europe to become a world-renowned Diva." In June 2006, the music video of her Korean song "My Name" became the first music video ever shown on MTV K, an MTV music channel directed at Korean Americans. Because of her wide appeal, BoA has appeared in advertisements for many brands. Among the brands she has promoted are Olympus, Nike, L'Oréal, Japanese cosmetic company Kosé, Skechers, Audio-Technica, and GM Daewoo. Four of her songs have been used as themes. "Every Heart: Minna no Kimochi" was used as the ending theme for the anime InuYasha; "Beside You: Boku o Yobu Koe" was used as the opening theme for the anime Monkey Typhoon; "Key of Heart" was the theme song for the Japanese release of Over the Hedge; and "Your Color" was the theme song of the video game Ninety-Nine Nights. Her widespread popularity has also made her a "cultural ambassador"; she has represented South Korea in inter-Asian musical events and has appeared in an Oxford University Press-published English-language textbook. From 2001 to 2007, BoA hosted Beat it BoA's World, a radio program on the Japan FM Network. In September 2004, BoA instigated controversy in Japan when she donated ₩50 million to a memorial project for Korean independence activist and nationalist An Jung-geun. BoA voiced Heather the opossum in the Korean and Japanese version of Over the Hedge. In 2008, Korean jewelry brand Ramee released Ramee by BoA, a line of jewelry designed by the singer herself. On June 9, 2008, BoA and nine other artists from around the world recorded an English cover of Wei Wei's "Dedication of Love". Produced by Roald Hoffmann and Brian Alan, the single was used to raise funds for victims of the Sichuan Earthquake.