Foster spilte keyboard i popgruppen Skylark, som hadde en hit med sangen i 1972. Han har jobbet som produsent for The Bee Gees, John Lennon, Michael Bublé, Clay Aiken, Josh Groban, Katharine McPhee, Céline Dion, Barbra Streisand, Kenny Rogers, Faith Hill, The Corrs, George Harrison, Ronnie Hawkins, Chicago (band), Earth, Wind & Fire, Chaka Khan, Filippa Giordano, Laura Pausini, Whitney Houston, Michael Jackson, Brandy, Luis Miguel, Fred Norris, Richard Marx, Mariah Carey, Destiny's Child, Vanessa Williams, Anne Murray, Olivia Newton-John, Andrea Bocelli, Deborah Blando, Lisa Marie Presley, Lara Fabian, Dolly Parton, Julio Iglesias, Gordon Lightfoot, Madonna, All-4-One, Ricardo Montaner, Al Jarreau, Kenny Loggins, Natalie Cole, Yolanda Adams, The Tubes, Peter Cetera og mange andre.