The process of stealing the head was, apparently, not pleasant, since decomposition had set in and the smell was strong. However, Peter and Rosenbaum succeeded in cleaning the skull and duly carried out their phrenological examination. Peter declared that "the bump of music" in Haydn's skull was indeed "fully developed". Afterward, Peter kept it in a handsome custom-made black wooden box, with a symbolic golden lyre at the top, glass windows, and a white cushion.

In 1820, Haydn's old patron Prince Nikolaus Esterházy II was inadvertently reminded by the chance remark of an acquaintance that he had forgotten to carry through his plan of having Haydn's remains transferred from Gumpendorf to the family seat in Eisenstadt. When the remains were exhumed, the Prince was furious to find that they included no skull, and quickly deduced that Peter and Rosenbaum were responsible. However, through a series of devious maneuvers Peter and Rosenbaum managed to maintain possession of the skull (Peter gave it to Rosenbaum, who hid it in a straw mattress, which his wife lay on during a search. Eventually he gave Prince Esterházy a different skull).

http://en.wikipedia.org/wiki/Haydn's_head