Are you looking for a local music player that fits in with your oh-so Material Android 5.1 custom ROM? Then let you fingers do the walking to Gramophone, now available on the Play Store. This stand-alone music app has been in private beta for some time, but now you can grab it without even messing with that awkward Google+ community invitation system. It's a free download for Android 4.1 or later.
Gramophone is fairly standard as far as music players go: album/artist/genre/playlist views, slide-out hamburger menu, search function. The only part of the interface that isn't immediately obvious is the "now playing" button that brings you to the main playback screen. It's the three-column icon next to the search button in the top right corner. When you're in other portions of the app the floating action button allows for a quick play or pause. On compatible builds of Android the navigation buttons and notification bar are automatically colored to match the album art of whatever song is playing at the moment.
In addition to what might be the purdiest music app available at present, your free download also includes both dark and light themes, Last.FM integration for album and artist information, notification and lockscreen controls, and a homescreen widget. Give it a try if you prefer your own music collection to streaming tunes.