I signed up with Music Xray about a month ago. It's quite simple to complete and earn, but like previous comments state it is a bit tricky reaching their $20 payout requirement. When I signed up they ask about my musical interest and since I enjoy a variety of genres, I just knew finding music for me to rate would be a breeze for them. The first week I received two alerts and another one the following week. My account has been pretty quiet ever since. I check back from time to time, thinking that maybe I overlooked the email sent telling me that I have new songs to rate, but still no luck.
If I had to rate this site I'd give it a 3 out of 10, simply because there's not enough material to rate. I also question their intentions to actually pay-out their subscribers. I wonder if they set their payout limit at such a high amount purposely to discourage the Impatient ones amongst us.
Best of Luck!