This app was mentioned in 4 comments, with an average of 2.00 upvotes
I'm using Pretty Good music player. It's very tiny <500KB. But It fits my needs.
Before that
GPM -> Shuttle+
I'd suggest Pretty Good Music Player. The interface is extremely simple, and has all the essential controls. Only thing is that there is no Album Art. It's also battery efficient. You can give it a try! https://play.google.com/store/apps/details?id=com.smithdtyler.prettygoodmusicplayer&hl=en