Stem Separator v6: DAW Export, Sections, Chords, Mashup, and 6 More

The Stem Separator just got its biggest upgrade yet — v6 — with ten new features that turn it from a separation tool into a full production workstation. Everything still runs on the local RTX 2070 (no cloud, no accounts, no per-track fees).

What's new

• 🎛️ DAW Session Export — export your separation as a ready-to-open Reaper .rpp project, or a universal stem bundle (stems + tempo/key/sections metadata + cues) that imports into Ableton, FL Studio, Logic, and Reaper. Section markers are baked in.
• 📊 Song Section Detection — auto-detects intro / verse / chorus / bridge / outro. A clickable color-coded timeline; click any section to export just that slice.
• 🎹 Chord Progression — detects the actual chord progression (not just the key) and exports it as a playable .mid file.
• 🔀 Stem Mashup — combine a stem from one track with a stem from another. Tempo and key are matched automatically so they lock together.
• ✨ Per-Stem EQ + Effects — low/mid/high EQ, reverb, compressor, and de-esser on any stem, with live preview and baked export.
• 🎵 Pitch Shift / Karaoke — shift any stem by semitones (high-quality Rubberband, duration preserved) for karaoke or matching a singer's range.
• 🎚️ Mix Presets — one-click Karaoke, Vocals-Only, Drums+Bass, and Instrumental, plus save your own custom mix recipes.
• 🔬 Multi-Model A/B — re-separate the same track with a different model and compare results side by side.
• 📋 Audio Validation — every track now reports duration, sample rate, peak, RMS, and approximate LUFS, with clipping/mono warnings.
• ⌘K Command Palette + PWA — a full command palette, keyboard shortcuts (space, 1–8 to mute stems, C, T), a light/dark theme, and an installable PWA.

Under the hood

The backend grew seven new endpoints (sections, chords+MIDI, validation, pitch, FX, DAW export, mashup, re-separate) built on librosa, Krumhansl-Schmuckler key/chord profiling, and ffmpeg's Rubberband for pitch. The frontend is still a single dependency-free HTML file. All ten features passed a full server regression suite plus a headless-browser E2E — zero console errors.

One item remains pending from last round: live MIDI transcription (piano-roll) needs a free HuggingFace token for the license-gated MuScriptor weights. The chord-progression MIDI export above works today without it.

Try it: Stem Separator