Stemquill is a free, open-source standalone application that converts audio stems into MIDI files. It writes one MIDI file per stem, ready to drag onto a track in any DAW, so drum, bass, keys and vocal parts can be replayed with different instruments, edited or rearranged.

Drums

Drum stems are split into kick, snare, closed hi-hat, open hi-hat, high, mid and low toms, crash and ride, each written to its own note. Drum maps are included for General MIDI kits (MT Power Drumkit, EZdrummer, Addictive Drums, Superior Drummer) and for pad samplers (FL Studio FPC, Ableton Drum Rack, MPC-style pads), and custom note numbers can be entered.

Melodic stems

Bass and vocal stems are transcribed as single-note lines. Guitar, keys and synth stems are transcribed as chords. An optional chord-detection add-on based on Spotify's basic-pitch, selectable in the installer, improves polyphonic accuracy.

Features

• Tempo detection from any stem.
• Optional snap to grid: 1/8, 1/16, 1/32 or triplets, or the original timing.
• Preview of each stem with built-in sounds before saving, with the original audio mixed in to check timing.
• Humanize control for timing and velocity variation.
• Per-stem sensitivity, humanize and drum selection, with an Apply to all option.
• Drag and drop of files or whole folders.
• Status for each stem showing when its MIDI is saved and when its settings have changed since.
• History of each conversion, with the drum hits or note range found.
• Command-line interface for scripting and batch use.
• Runs fully offline; audio is never uploaded.

Input formats

WAV, MP3, FLAC, AIFF, OGG and M4A.

System requirements

• Windows 10 or 11 (64-bit), using the installer.
• macOS and Linux: Python 3.10 or newer, installed with pipx.

Pricing

Free, with an optional pay-what-you-want donation. Released under the MIT license; source code is available on GitHub.

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