If you haven't noticed, BlackBerry has removed the music and video sections of BlackBerry World. This comes as announced way back when on June 18th, 2014, when the news came out that BlackBerry had partnered with Amazon to provide apps to BlackBerry 10. In that press announcement, BlackBerry said that they would cease music and video services in BlackBerry World and as of today, they have followed through with that announcement.
So, your music resources are temporarily gone for now. What is a person to do? Well one recourse for you audiophiles is the 7digital Music Store for BlackBerry. This is the Android port of their application to BlackBerry World. You may have/have had 7digital on your BlackBerry PlayBook. This is the same service.
You can download 7digital for your phone for free in BlackBerry World here.