A clean and simple universal music widget for Android 4.4+.
Ubiquity should work with any music player that displays controls and album art on the lockscreen (which is most music players, though some implement it poorly).
If you switch between different music players, you don't need to switch widgets. Just stop playing music in one app and start in another and the widget should switch.
As of version 2.0.3, all plus features are free and the source code is available on GitHub (github.com/jathak/musicwidget).
This widget will not work until you go to Security>Notification access in settings and check "Ubiquity Music Widget"