In Felwinter Peak, there is an Iron Temple located at the top of the area. There are 6 bells here, 1 situated right above you as you enter the temple and 5 located on the other side in succession. For this achievement you will only need to play 5 bells.
Treat the singular bell as bell #1. When facing that bell, look to the left hand passage, and you'll find five more bells. From the first bell you come to, treat them in succession as #2, #3, #4, #5, #6. You must play the bells in this order:
1 2 3 1 5
4 3 2 3 1
You need to do this in the same tempo as the theme, so you will need at least 2 players in a fireteam. Running solo and playing the bells will not work. Have one player play bell #1, while the other sprints between #2 to #5. With some practice you should be able to snatch the achievement
For an image with explanation, check the image below (couldn't find the source of the image, sorry!)http://imgur.com/a/IXS7Q
Videoguide from Maka91Thank you to Mikeyoligy and https://www.trueachievements.com/XpD+Pielord.htm for the confirmation that the bells listed in the guide now are the only ones needed