Building a Music Practice App with AI Stem Separation (Python + React)

Learning an instrument by ear is one of the most valuable things a musician can do. It's also frustrating when the bass is buried under the full mix. AI stem separation makes this dramatically easier: isolate the instrument you're learning, slow it down without changing the pitch, and loop the 4-bar phrase you keep missing. Here's how to build a lightweight practice tool that does exactly this. What You'll Build A small full-stack app with: Python backend that accepts an audio URL or file upload Stem separation via Demucs or API Time-stretching (slow down without pitch shift) Section looping A minimal React frontend # Backend pip install fastapi uvicorn demucs librosa soundfile requests pyrubberband numpy # For the API path instead of local Demucs pip install requests # Frontend npm create vite@latest practice-app -- --template react cd practice-app && npm install wavesurfer.js axios Backend: Stem Separation + Audio Processing main.py import io import subprocess import tempfile from pa