When entering the Bell Choir, after speaking to Bell Maestro in Lions Arch, players are placed into groups of 3 for the upper, lower or middle parts. When the Bell Choir begins you are given six songs, with the songs gradually increasing in difficulty as you play. If you hit too many wrong notes you'll begin to lose health and points (you start with 100 points) and will be kicked from play if your health eventually reaches zero. You can recover your health by hitting the right notes or talking to the snowman after being removed from the stage.
There are 8 lanes in total that you will be responsible for, with your skill bar split between each corresponding lane (1-4 and 6-9 on your keyboard). At first I tried using just 1-4 keys and using my mouse on the others but its best to place both your hands over the correct keys. When the musical orbs begin to move down your lane you will need to strike the note when it comes into contact with the inner blue circle. If you hit the note too soon you'll miss and lose health. If you hit too late, it won't count and you'll still lose health.
As mentioned previously, the starting notes will come down relatively slowly and can be hit easily but at later stages they move down incredibly fast giving you very little time to react. Depending on your final score will determine how many Personlized Wintersday Gifts you receive. Having the lowest points sees you receive 1 gift while high scores see you receive as many as 4. I'll freely admit that I found this entire mini game more difficult than the Halloween Clock Tower. I never was very good at Guitar Hero.
Become the Bells: Completing 10 songs in Bell Choir Ensemble – 10 points
Ring in the Season: Playing 500 correct notes in Bell Choir Ensemble – 10 points
Both achievements will contribute towards the Apprentice Toymaker achievement.