A strict vegetarian and a follower of Sant Mat, Lange has not given an interview for decades and prefers to live a secluded life, primarily in Switzerland. He is known for his work in the studio and innovations in multitrack recording.
Robert John Lange was born in Mufulira, Northern Rhodesia (now Zambia) and raised in Durban, Kwa-Zulu Natal, South Africa. His mother came from a prosperous family in Germany, and his South African father was a mining engineer. Nicknamed "Mutt" at an early age, Lange grew up a fan of country music, in particular the singer Slim Whitman. Sent to study at Belfast High School in South Africa, he started a band in which he played rhythm guitar and sang harmonies. After his national service (1966–1967) he formed the band Sound Reason in 1969. In 1971 he started the group Hocus, recording one album and releasing 5 seven-inch singles. He eventually married Stevie van Kerken (a.k.a. Stevie Vann) and moved to England. The marriage broke down in the 1970s. Whilst still married, Lange began seeing Belfast-born employee Oonagh O'Reilly, a relationship that lasted five years.
In 1978, Lange wrote and produced Ipswich Town's FA Cup final single Ipswich Ipswich Get That Goal, his connection with the club being due to their South Africa-born player Colin Viljoen. The song is derived from a previous recording Give That Thang To Me by Paul Jones (1977), with some parts rearranged and new lyrics.
After Hysteria, Lange bowed out of working with Def Leppard while they were at their peak. He would return to work with them years later in a more limited role in 1999, co-writing three tracks for their album Euphoria. One of these songs, "Promises", was a Number 1 hit on the mainstream rock charts for the band.
After hearing Shania Twain's material, he got in touch with her and they spent many hours on the phone. They finally met six months after the initial contact and were married on 28 December 1993. Because Lange is a teetotaller, they had non-alcoholic champagne at their wedding. Lange also had the song "(Everything I Do) I Do It for You" performed as a sign of his dedication. In August 2001, their son Eja (pronounced "Asia") was born. On 15 May 2008 a spokesman for Mercury Nashville announced that Twain and Lange were separating after Lange had an affair. Lange began seeing Twain's best friend, Marie-Anne Thiebaud. The couple divorced in June 2010, and Twain is now married to Thiebaud's ex-husband Frederic.