How to Isolate Vocals in Python: API vs Demucs vs Audacity CLI (2026)

I keep seeing "how to isolate vocals" questions on Stack Overflow where the accepted answer is five years old and recommends Spleeter. Let's fix that. Here are three methods that actually work in 2026, with working code for each, and SDR benchmarks so you know what quality to expect before you commit to one. What You'll Learn ✅ The fastest way to isolate vocals with no local setup (API, ~5 lines of Python) ✅ How to run Demucs locally for best quality ✅ How to automate Audacity via CLI for legacy workflows ✅ SDR scores across all three methods on the same test tracks ✅ Which method fits which use case Prerequisites pip install requests librosa soundfile mir_eval numpy For Method 2 (local Demucs): pip install demucs torch For Method 3 (Audacity CLI): # macOS brew install audacity # Ubuntu sudo snap install audacity Method 1: Online API (Fastest, No Setup) Best for: Prototypes, web apps, when you don't own a GPU, or when you need results immediately. The easiest path is to call a stem sep