Here are a few well-known sites you can use to download audio from YouTube videos—just paste the YouTube link and you can convert to MP3 instantly: AudioCleaner (
audiocleaner.ai), YTMP3, Y2Mate, and KeepVid.
These sites are free to use and don't require you to install anything—just make sure to only download content you have the rights to, since saving copyrighted material is generally not allowed.
Stay clear of sites that bombard you with pop-ups or ask for weird permissions, since those can be risky.