Xvf Player is a simple audio player
that plays all audio files in a folder,
or an audio file after a selection in a filemanager.
This is the only Music Player I use for Android.
You can get the APK here.
To play a folder/song, click on the first line of the Player (folder information) to select.
Long-press play button to pause player, press to continue.
Remember to Allow management of all files (app Storage permission).
Sorry for the lack of further information, I will fill this ASAP.