How to download music from an app for iPhone 4S?

I've been downloading music from a free app for my iphone but I can only listen to the music in the app, is there a way to put the music into the music folder? Or a free music app that can download music and store it in the music folder?

I use TuneShell app, and the websites you can use: itunesmusik.info, datpiff.com, or mp3skull.com.
But this is why android is better, iPhone is not going to let you freely do anything. Unless you jailbreak but still even jailbreak is not worth it these days. For Jailbroken users you can get Music Box, Movie Box, Bridge, ProTube on cydia.

Download mp3 skull
when you open the app you have to type mp3skull.com in the search box

Use this apps.Download on PC and before download you need itunes.Download done and import your music on Music
https://shrinkonce.com/download.php?file=11jd3