"Blunt" is in the thesaurus under "simple."
It plays MP3s in folders.
Click on the 'folder play' icon to the left of a directory, and it plays the MP3s in that directory. Click on the directory name, and it enters the directory. Click on the 'folder play' icon to the left of a filename, and it plays all the MP3s in the folder starting at that one. Click on the file name, and it plays just that MP3.
I used FolderPlayer for years, but it's become rather over-featured and it has features to make it simple again, but those features are buggy. Adding simplicity as a feature is an oxymoron.
I used SimplePlayer for years, but it has two bugs: sometimes the file-selection UI goes unresponsive; sometimes it stops playing in between tracks if the screen is off. It is open source, so I wanted to fix it, but it has a ton of extraneous dependencies and code.
I looked for a while and I think those may be the two best folder-based MP3 players on the Play Store.
Because I like to rant at length about things no one cares about, let me add that it's a real travesty that so many apps are written to such a poor engineering standard. I can't brag about BluntMP3, but have you seen the other guy?
BluntMP3 is a minimal Android wrapper around Underbit's libmad (MPEG Audio Decoder). BluntMP3 is Copyright 2017 by Greg Alexander, to be distributed under the terms of the GPL version 2.
Complaints? Email me:
To get the source:
git clone http://galexander.org/git/bluntmp3.git