I have coded the website to download mp3 from youtube video. I'm basically using APIs for MP3 and MP4 conversions and everything works fine …
The website is "youtubetake.com" and you do not need to visit it. While watching a YouTube video, enter "take" between "youtube" and ".com" to download MP3
Check out this animation.
Website working on mobile phones. I made the version of m.youtube.com … also.
Where to promote this website? I think maybe it's better to promote it like explaining to people how to use it. Something like "YouTube tips and tricks" ….