West's musical career has been defined by frequent stylistic shifts, and has seen him develop and explore a variety of different musical approaches and genres throughout his work. When asked about his musical inspirations, he has named A Tribe Called Quest, Stevie Wonder, Michael Jackson, George Michael, LL Cool J, Phil Collins and Madonna as early interests. He has further described musician David Bowie as one of his "most important inspirations," and named producer Puff Daddy as the "most important cultural figure in my life." Early in his career, West pioneered a style of production dubbed "chipmunk soul" which utilized pitched-up vocal samples, usually from soul and R&B songs, along with his own drums and instrumentation. His first major release featuring his trademark soulful vocal sampling style was "This Can't Be Life", a track from Jay-Z’s The Dynasty: Roc La Familia. West has said that Wu-Tang Clan producer RZA influenced him in his style, and has named Wu-Tang rappers Ghostface Killah and Ol' Dirty Bastard as inspirations. RZA spoke positively of the comparisons, stating in an interview for Rolling Stone, "All good. I got super respect for Kanye [...] [he] is going to inspire people to be like him." West further developed his style on his 2004 debut album, The College Dropout. After a rough version was leaked, he meticulously refined the production, adding string arrangements, gospel choirs, and improved drum programming.