SolPlayer Tune от foresthill

SolPlayer Tune converts the audio of the YouTube video you are watching to alternative tunings in real time — entirely inside your browser.

■ How to use
1. Open any YouTube watch page
2. A "♪ 440Hz" button appears below the video
3. Tap it to open the tuning panel and pick 432Hz (or 444Hz)
4. Pick "440Hz standard" to return to the original, unprocessed audio

■ Features
• One-tap presets: 440 (standard) / 432 / 444 Hz
• Custom frequency with up to 10 decimal places (200–999 Hz)
• Save your own frequencies as personal presets
• Selecting 440Hz fully bypasses processing (zero latency, zero overhead)
• Works on desktop Firefox and Firefox for Android

■ Privacy
No data collection, no analytics, no network requests. Audio is processed in real time and never recorded, stored, or downloaded. Your settings stay in your browser.

Note: while conversion is active, audio lags ~0.2–0.3s behind the video (buffering required for real-time pitch shifting). This is expected and does not affect music listening.