In 1968, Marvin returned to the top of the charts as a solo act with the Norman Whitfield-penned "I Heard It Through the Grapevine". The song, originally recorded in 1967, was initially blocked from release since Berry Gordy disapproved of the song. Instead, one of its cover versions by Gladys Knight & the Pips was released, and it ended up reaching number-two. Whitfield was determined to get Gordy to release Marvin's, and in October 1968, Motown finally issued "Grapevine" as a single where it eventually reached number-one in December of that year, it also reached number one in the U.K. and became the biggest-selling single in Motown history during the sixties. During this period, Marvin used his "Grapevine" success to produce a collection of singles for his background group the Originals. Those songs, "Baby I'm for Real" and "The Bells" became top 40 recordings. After two more top ten hits that followed, Marvin began working on a more personal production. Inspired by Tammi Terrell's death, his brother Frankie's Vietnam stories, footage of the Vietnam War and race riots in the U.S., Marvin's success with his first productions and a rough draft of a song composed by Four Tops member Obie Benson, Marvin recorded an introspective single titled "What's Going On". Like "Grapevine", Motown refused to release it due to it being "uncommercial" and "risky" since Gordy could not find a song to match anything with and also because Gordy was against anyone in his company to talk openly about serious issues. In spite of releases by the Temptations, the Supremes and Edwin Starr, which opened about inner city struggle, illegitimate pregnancy and wars respectively, Motown was afraid the song would ruin Marvin's squeaky-clean teen pop image. Marvin, confident in his own abilities, stood his ground, and in January 1971, the song was released quickly becoming a hit single reaching number two on the Billboard pop chart and number one on the Cashbox pop chart, also hitting number-one on the Billboard R&B chart. A follow-up album of the same name was quickly released that May and with accompanying top ten singles "Mercy Mercy Me" and "Inner City Blues", songs that also talked about social issues including environmentalism, the album sold over a million copies and permanently made Marvin one of the first independent artists on the label. Inspired by Marvin's success, Stevie Wonder refused to renew his contract with Motown in May 1971 after releasing the non-Motown approved "Where I'm Coming From", an album that also dealt with social issues. In 1972, Motown signed Marvin to a $1 million contract, making him at the time the highest-paid black recording artist in music history. Marvin celebrated the contract by releasing the pro-political single "You're the Man", which attacked the Nixon administration. Moving from Detroit to Los Angeles that year, he recorded the soundtrack to the movie, "Trouble Man". The soundtrack and its title track became top twenty and top ten hits on the charts respectively. In 1973, Marvin dramatically changed direction from social topics to sexual politics with the release of "Let's Get It On". The song became Marvin's second number-one Billboard hit and was the biggest-selling R&B single of that year. Its subsequent album became another critical milestone as "What's Going On" had been and with his new look as a wool hat-wearing, studded jean outfit, bearded "messiah", Marvin had become an icon of early seventies soul music.