Former R Kelly collaborators Lady Gaga and Jay-Z are among the musicians who have declined to be interviewed for a documentary series on the R&B star’s alleged history of abuse against young women. “It was incredibly difficult to get people who had collaborated with Kelly to come forward,” Surviving R Kelly executive producer dream hampton told the Detroit Free Press. Kelly has frequently denied the allegations.

Kelly collaborators Erykah Badu, Céline Dion and Dave Chappelle turned down interviews, said hampton, and Questlove, drummer with the Roots, also allegedly declined to participate. “I remember Ahmir [“Questlove” Thompson] was like, ‘I would do anything for you but I can’t do this’,” said hampton. “It’s not because they support him, it’s because it’s so messy and muddy. It’s that turning away that has allowed this to go on.”

In now-deleted tweets, Questlove claimed he declined an interview because he thought he was only being asked to praise Kelly and not condemn him. “I always thought Kels was trash,” he wrote. In another deleted tweet, hampton disputed Questlove’s claims, adding: “I told you I need Black male allies.” The Guardian has contacted representatives for Lady Gaga, Jay-Z, Badu, Dion, Chapelle and Questlove.

In the end, John Legend and US R&B artist Stephanie “Sparkle” Edwards were the only musicians interviewed in the documentary series. hampton described Legend as a “hero” for speaking out against Kelly. Legend responded on Twitter: “To everyone telling me how courageous I am for appearing in the doc, it didn’t feel risky at all. I believe these women.”

He added: “These survivors deserved to be lifted up and heard. I hope it gets them closer to some kind of justice.”

On Twitter, hampton said she hoped “the absence of celebrities really isn’t the takeaway today. Even if they’d said yes, the non-celebrities would’ve been featured more than them.” More than 50 people are interviewed in the documentary, including Kelly’s ex-wife, Andrea Kelly, who has accused him of numerous incidents of domestic violence, ex-girlfriend Kitti Jones, who has accused Kelly of physical and mental abuse, and Time’s Up founder Tarana Burke.

In early December, the New York City premiere of the series was cancelled after an anonymous shooting threat was made to the venue. Andrea Kelly told Rolling Stone that she believes Kelly “had this shut down”. Kelly’s legal representatives had threatened to sue the US channel Lifetime if it aired the series, claiming that the documentary is littered with false allegations and that its subjects are defaming Kelly for personal gain.

The first two episodes of the six-part series were shown on Lifetime on 3 January, and focus on the beginning of Kelly’s career, prior to the emergence of a 2002 sex tape that would lead to his trial and acquittal.

The first episode details Kelly’s relationship with the late R&B singer Aaliyah, including allegations that Kelly, then 27, was seen having sex with the teenager on a tour bus, and that forged paperwork led to their illegal marriage when she was 15. Kelly’s former tour manager and personal assistant also alleges that Kelly impregnated the young singer, who died in a plane crash in 2001. He denied inappropriate behaviour with her.

Two women claimed that Kelly was sexually interested in girls as young as 14. Sparkle recalled Kelly grooming her niece when she was 12. Singer Jovante Cunningham claimed that Kelly made teenage girls perform sexual acts in public, and had sex with a teenage girl in the studio with other people present. Lizzette Martinez, who claimed Kelly impregnated her while she was in high school, said that Kelly told her to “perform sexual acts while his friends were in the back seat”.

Andrea Kelly claimed that her ex-husband involved her in an elaborate wedding ceremony without her prior knowledge. She described this as among the first times she realised he was “controlling”.

In 2000, Chicago Sun Times reporter Jim DeRogatis was the first journalist to report on allegations that Kelly had sex with teenage girls. In 2002, Kelly was indicted on 14 counts of child pornography. He was cleared on all counts in 2008. It would take a decade – during which Kelly enjoyed chart success, cult acclaim for his spoof series Trapped in the Closet, and tastemaker support – for claims of Kelly’s sexual impropriety to find public traction. In July 2017, DeRogatis reported for BuzzFeed that Kelly was holding women in a “sex cult”, a story denied by Kelly that led to more women accusing him of sexual and physical abuse, and the decline of his reputation.

Kelly has consistently denied the allegations against him, including those of inappropriate behaviour with minors, and described as “too late” the #MuteRKelly campaign, which urges record labels, promoters and other parties with financial interests in Kelly to sever their ties with him. In July 2018, he released a 19-minute song, I Admit, in which he denied the allegations but “admitted” to sleeping with fans and having parents “push” their daughters on him “to get paid”. He also reiterated claims that he was sexually abused by a family member as a child.

Lifetime will show the remaining four episodes of Surviving R Kelly on 4 and 5 January.