Fenix Flexin Denies Faking His Vocals With AI—But Treblo's Own Detector Just Snitched on Him

There's something inherently absurd about Fenix Flexin putting on a nasally, faux-"raised on the streets of Manchester" delivery — this is the same LA rapper best known for twerk anthems and prescription-pill punchlines, suddenly channeling something that sounds like Morrissey. "Rubberz" went viral on Instagram and climbed toward the Billboard Hot 100, but the comment sections and social media timelines simultaneously erupted into a debate about the ethics of AI-assisted vocals.

Facing the accusations, Fenix initially dug in hard. "No sirrrrrrr, recorded the same way I always do!" he replied to one user. "Only difference is I added auto-tune reverb, and I'm doing a British accent." As a current member of West Coast rap collective Shoreline Mafia (Pitchfork initially reported he'd left the group, then issued a correction), Fenix looked like he might genuinely ride this brazen denial all the way to a summer-anthem crown through sheer stubbornness.

But two things blew up his story. Last Thursday, producer Medasin, who bills himself as a "sound scientist," posted a point-by-point breakdown on Instagram outlining features in "Rubberz" that suggested AI generation. The most damning piece of evidence: a file name suffix — "Sonauto.mp3" — that Medasin spotted in an old video posted by Fenix. Sonauto was the former company name of generative AI platform Treblo, before it rebranded just two days before "Rubberz" dropped. Medasin also used a simple prompt on Treblo to generate his own track, and it sounded eerily close to the single.

Fenix denied it again, sending Medasin a video that appeared to show separated vocal and instrumental stems, apparently to prove the track couldn't have been fully AI-generated. Medasin wasn't convinced — he and other users pointed out that widely available stem-separation tools can automatically split any finished song into vocals, instrumentation, bass, and drums. Fenix soon deleted the video and stopped responding.

As the controversy spread, Treblo cashed in on a flood of free exposure thanks to its accidental spokesperson, Fenix Flexin. Perhaps that's exactly why the platform made its move last Sunday night, rolling out a new tool called "Was This Made With Treblo?" According to Wired, the company claims this AI-detection tool has an extremely low error rate. The results for "Rubberz" weren't pretty — the tool flagged the track as "highly likely made with Treblo," and the same report returned similar results for several tracks on labelmate Tyga's new album. The tool's open-source code has been made public, but it hasn't yet undergone independent review.

When Wired reached out for comment, Treblo co-founder Ryan Tremblay didn't exactly throw Fenix a lifeline — if anything, he all but confirmed what everyone already suspected: "It looks like someone used our model to find a sound that resonates with millions of people, and that's exciting." One line, and what looked like a scandal to everyone else got reframed as a product win.