First of all, you can laugh.
A student was one night examining an image of painting by Hieronymus Bosch and to her amusement she found “…music written upon the posterior of one of the many tortured denizens of the rightmost panel of the painting which is intended to represent Hell.” The finding went viral and it became this ‘hell butt song’ which I think most people would find it amusing.
Below is the painting I was talking about. It is a triptych from 16th Century. Now, for those unfamiliar with tryptic tradition, triptych is one of the most captivating tradition of medieval church. The triptych would be folded and closed for viewing and only available once a year in an auspicious date and people would travel and gather in church to see, be mesmerised on the pictures in awe and magical feeling. A triptych would depict scenes and stories from the Bible.
The hymn it self could be found on the lower right of the painting, on someone’s buttocks who is lying on his chest underneath the lute. You can see a creature from hell seems to be reading from this persons buttocks and chant the hymn. So, since the finding there are a number of people who tries to reconstruct it. This video I found below is from a Russian Quite fascinating!
To read more about the painting itself, this essay on Khan Academy provides a good explanation on the painting.