Better Melody has a twist on the traditional rating site:
Pick the better song: instead of rating a song from 1 to 5 or 1 to 10, you pick the better of two songs.
Song's score changes: The songs are then rated based on the ELO system, famously used in the chess world. The winning song's score goes up, the losing song's score goes down.
Unlike other systems that are based on a fixed number of matchups won or lost, the ELO system takes into account the difference between songs and adjusts scores accordingly.
For example, if you pick a low-scoring song over a high-scoring one, their ratings change more than if you picked a medium-scoring song over another medium-scoring song.
The ELO system is considered better than other rating systems because of its accuracy and long-term stability.