Music app for cached videos

[ArsovV]

I've been using PlayTube for years now because it cached my videos and when I lock the phone or switch between apps, the music keeps playing.
I upgraded to 9.3.3 and now the app still caches videos but when I lock the phone or when I switch apps, it pauses the song.
Which apps do you use for playing music that can do the above?

 

[ArsovV]

After a couple of days of searching, I found iMusic. It caches the videos so I can play the music even without an internet connection and the app will keep playing music if you lock your device or switch between apps