How to get audio from YouTube onto my iPhone?

There's this song on youtube that I like, but it's a mash-up, so it's not on iTunes or Spotify. Is there a way that I can(legally) get the audio or video onto my phone so I'm not using wi-fi while listening to it? And I would prefer not to jailbreak my phone.

Well it's not complicated if you have a Mac ( I hope you have one )…

You first need QuickTime Player, here's the link for Windows users (mac already has it) http://support.apple.com/...m/kb/DL837

Then you download Soundflower
Mac: https://www.macupdate.com/app/mac/14067/soundflower
I don't know in windows

You change the sound input and output to Soundflower (2ch)

You go to QuickTime and select Audio recording, and change the microphone preference to Soundflower (2ch), and start recording

That way you'll only record the sound that your computer does but not the sound that it's around you, so better don't touch the computer while recording

hope it helped if you're a Mac user and if not sorry.___.