iPhone Best app (free if possible) to convert YouTube videos and convert to MP3's on phone?

[Boca]

Best app (free if possible) to convert YouTube videos and convert to MP3's on phone? thanks for any suggestions.

 

[now i see it]

There used to be an online service that would download YouTube vids and convert them to MP4 to download directly to your device, but Google shut them down.
There's no iOS App available (the last time I looked) that can do it either.
Maybe things have changed, but there wasn't anything available 9 months ago

 

[Boca]

Thank you for your info.