Murmur

Murmur is an open-source macOS voice keyboard.

Hold Fn, speak, release — text appears where your cursor is.
Hold Fn + Control to rewrite with AI.
Select text first to use it as context.

English-first. Free. Open source.

Website: https://murmur.luciana.digital

Why it exists

Typing interrupts thought. Murmur lets you speak into the app you are already using.

Use it for:

• Slack replies
• emails
• notes
• tasks
• AI prompts

How it works

Action	Result
Hold Fn	local dictation
Hold Fn + Control	AI rewrite
Select text + Fn + Control	context-aware rewrite
Release	paste into the active app

Raw dictation runs locally with WhisperKit. AI mode sends text, not audio, to OpenAI.

AI rewrite mode also supports:

• Style Profiles for Email, Work, Casual, and Other apps
• Tone and length preferences per profile
• A Dictionary UI for names, tools, commands, and mishearing fixes

For noisy rooms, open Settings → Speed vs Quality and switch from Fast to Noisy room. Murmur shows model download progress in the floating controls, menu bar tooltip, and Debug. If a larger model is not ready, it falls back to the best available local model.

Model options

Choose a local transcription model in Settings → Speed vs Quality → Optimize.

Setting	Model	Download size	Best for	Languages
Fast	openai_whisper-base.en	~142 MB	Lowest latency in quiet rooms	English only
Noisy room	openai_whisper-small.en	~244 MB	Better English accuracy with background noise	English only
Best quality	openai_whisper-large-v3-v20240930_turbo_632MB	~632 MB	Difficult audio, accents, and noisy environments	Auto-detects supported languages

Fast and Noisy room use English-only models. Best quality enables automatic language detection for supported languages.

Install

Requires macOS 14+. Apple Silicon recommended.

curl -fsSL https://raw.githubusercontent.com/LucianaMa1/murmur/main/install.sh | bash

Then grant:

• Microphone
• Input Monitoring
• Accessibility

Add an OpenAI API key in Settings for AI rewrite mode.

Build from source

swift build
./build.sh
open dist/Murmur.app

Repo structure

Sources/       macOS app source
Resources/     app icon assets
launch-site/   public website
scripts/       icon generation helper

License

MIT