LAラッパーのFenix Flexin、楽曲「Rubberz」へのAI使用をほぼ認めるFenix Flexin isn’t even denying using AI to make ‘Rubberz’ anymore

The debate over undisclosed artificial intelligence in music has a fresh flashpoint. Los Angeles rapper Fenix Flexin appears to have admitted that an AI tool was involved in making "Rubberz," an 80s synth pop-themed track, after days of public accusations from producer Medasin. The episode matters because it lands at the intersection of two fast-moving trends: the rapid improvement of generative music software and a growing insistence from artists, producers, and listeners that any AI involvement be disclosed up front.

According to The Verge, Fenix Flexin's near-admission followed videos posted by Medasin claiming that a tool called Treblo, formerly known as Sonauto, was used to create the song. Treblo belongs to a growing category of text-to-music systems that can generate instrumental arrangements, vocal-style passages, and genre-specific production from written prompts. Reports indicate the company itself was drawn into the conversation, underscoring how quickly disputes like this can pull in the platforms behind the technology as well as the artists using it.

What makes "Rubberz" notable is less any single technical trick and more the pattern it represents. The track's 80s synth pop styling is exactly the kind of clearly defined aesthetic that modern generative models handle well, since such systems are typically trained to reproduce recognizable genre conventions on demand. That capability is precisely what has made disclosure such a contentious issue: when a tool can convincingly emulate a period sound, listeners often cannot tell by ear whether a human or a model produced a given part.

Fenix Flexin has built a following in the LA rap scene, and his apparent reliance on AI for a stylistically distinct release has drawn attention partly because hip-hop has historically prized authorship, sampling craft, and producer credits. The controversy appears to hinge less on the legality of using such tools and more on whether their use should have been acknowledged before Medasin's videos surfaced. That distinction, between using AI and disclosing it, is at the heart of many recent industry disagreements.

The dispute fits into a broader wave of tension around generative music. Services such as Suno and Udio have drawn both large user bases and significant legal scrutiny, including lawsuits from major record labels over how their models were trained. Treblo's rebrand from Sonauto reflects how young and volatile this segment remains, with tools frequently changing names, features, and business models as they seek footing in a crowded market. Streaming platforms, meanwhile, have been weighing policies on labeling AI-generated content, and some have moved to remove or flag uploads that appear to be machine-made without disclosure.

For working musicians, the stakes are practical. Credits determine royalties, publishing splits, and reputations, so an undisclosed AI contribution can complicate who is owed what and who can claim creative authorship. Producers like Medasin, who make part of their living from demonstrable skill in arrangement and sound design, have an obvious interest in surfacing cases where they believe automated tools were passed off as conventional production. At the same time, many artists argue that AI is simply another instrument, comparable to samplers or synthesizers that faced similar skepticism in earlier eras.

It remains unclear exactly how much of "Rubberz" was generated versus arranged or edited by human hands, and Fenix Flexin's comments appear to stop short of a detailed accounting. That ambiguity is itself part of the story, because current tools rarely leave obvious fingerprints, and there is no widely adopted standard for documenting where a model's output ends and a person's edits begin. Efforts to develop watermarking, provenance metadata,