The App has some cool interface and features which you are looking to have in a YouTube Player Apps. The App is developed by XDA Developer who goes by name Deep Gaurav. You won’t find this App on Play Store due to Google’s ToS which won’t allow Apps to download media from YouTube. It is the best Android Music Player App for YouTube. Built with all the features needed in a Player App.
The App is completely free, lightweight and doesn’t ask for any weird permissions. Thus it functions similar to an Online Music Player, all you need to do is search for your favourite song and start enjoying the music directly from Mammoth Library of YouTube. Apart from being free it also doesn’t show any Ads and has no API.
MusicPiped is a free open source music player which lets you stream songs directly from YouTube.
