Music Sheet

There are four different Music Sheets, which all look the same:
*Music Sheet (First Verse), dropped by Novices of the Cult.
*Music Sheet (Second Verse), dropped by Acolytes of the Cult.
*Music Sheet (Third Verse), dropped by Adepts of the Cult.
*Music Sheet (Fourth Verse), dropped by Enlightened of the Cult.
In addition, Grandfather Tridian drops all four. Learn all four to get the achievement Chorister