Music Box App is a fully functional dropbox music player app for iOS:
Turn your dropbox into a personal cloud music player in seconds.
User log in through dropbox.
Automatically sync with dropbox, so if you remove files from dropbox, it will remove in the app also.
Stream your music files from dropbox
Or download to your phone for offline listening
Playlist for all the mp3 or other common sound formats
You can control through control center
Now you can take your own musics anywhere.