Tabber

Chrome extension + local Python backend that captures guitar audio from browser tabs and converts it to Guitar Pro tablature (.gp5 files).

Architecture

Chrome Extension (MV3)          Local Python Backend (FastAPI)
┌─────────────────────┐         ┌──────────────────────────────┐
│ Popup UI            │         │ POST /transcribe/url         │
│  - URL mode button  │───────→│   yt-dlp download + transcribe│
│  - Record mode btn  │         │                              │
│                     │         │ POST /transcribe/audio       │
├─────────────────────┤         │   WebM upload + transcribe   │
│ Service Worker      │         │                              │
│  - tab info         │         │ GET /health                  │
│  - stream ID mgmt   │         ├──────────────────────────────┤
├─────────────────────┤         │ Transcription Engines:       │
│ Offscreen Document  │         │  1. Klangio API (primary)    │
│  - MediaRecorder    │         │  2. Basic Pitch + PyGuitarPro│
│  - audio capture    │         │     (open-source fallback)   │
└─────────────────────┘         └──────────────────────────────┘

Setup

Prerequisites

• Python 3.10+
• uv (or pip)
• ffmpeg (system install)
• Chrome browser

Backend

cd backend
uv sync          # or: pip install .
uvicorn main:app --port 8765

Configuration

Create backend/.env or set environment variables:

Variable	Default	Description
KLANGIO_API_KEY	(empty)	API key for Klangio engine
DEFAULT_ENGINE	klangio	klangio or opensource
PORT	8765	Backend server port

Chrome Extension

1. Open chrome://extensions/
2. Enable Developer mode
3. Click Load unpacked → select the extension/ directory

Usage

1. Start the backend server
2. Navigate to a tab with guitar audio (e.g. a YouTube guitar video)
3. Click the Tabber extension icon
4. Choose an engine and either:
   • Transcribe from URL — sends the page URL to the backend (works with YouTube, etc.)
   • Record Tab Audio — captures live audio from the tab, then transcribes when stopped
5. A .gp5 file downloads automatically, named after the tab title

Transcription Engines

Klangio — Commercial API with high accuracy. Requires an API key from klang.io.

Open-source — Uses Basic Pitch for audio-to-MIDI detection, custom fret assignment, and PyGuitarPro for GP5 generation. No API key needed.