by Nerd Person Thing
Requires neither premium nor root.
A relatively simple script that allows you to save any YouTube video as an MP3 file with a filename of your choice. Read the diructions below if you have problems.
-Works as of 2017/4/7 for most YouTube videos (fails some of the time for more obscure videos).
-On many devices, Android prohibits apps like Automate from writing files such as MP3s to your SD card, so you might not want to choose a save location there unless you know your particular phone doesn't have this restriction.
-And if you find this useful, hey, maybe you could consider being a cool dude/dudette and giving the flow an honest rating. Much appreciated!
Directions for use: When you first launch the flow, it will ask you to choose a folder to save the MP3s to. (When you launch it again, you won't have to do this - it'll be saved.) It will then begin monitoring the YouTube app for the use of the share button. Find the video you want to download the mp3 of, click "Share," and select the "Automate flow" option. It will then prompt you to enter the filename, and once you do that, it will automatically download the file to your "Music" folder. Ta-da!
Version 2 (2017/3/24): Fixed a minor bug.
Version 3 (2017/3/27): Now allows the user to choose a save location.
Version 4 (2017/3/27): Allows users to RESET the file location as well, if needed.
Rate and review within the app in the Community section.