Last week a friend sent me a voice memo. "I found this incredible bass line in an old soul track," he said, "but I can't isolate it without paying $30/month for some cloud service that wants my email, my credit card, and probably my firstborn." He's not wrong. The audio stem separation landscape in 2026 is a mess of subscription walls and cloud uploads. Most tools send your audio to a remote GPU, process it, and send back the stems. You get results in minutes, sure, but your unreleased remix idea now lives on someone else's server. I wanted to see if the entire pipeline could run locally, in a browser tab, with zero network requests after the initial page load. Turns out it can. What stem separation actually is For those unfamiliar: source separation (also called demixing or unmixing) is the process of decomposing a mixed audio signal into its constituent sources. A typical pop track is a sum of vocals, drums, bass, and everything else (guitars, synths, keys, strings). The AI's job is to reverse that sum.…