|Fig. 1 - Sumerian Bronze Bull's Head, Michael C. Carlos Museum|
The bull often represented the god An, who was a fertility god and also was considered the source of the king's power and right to rule.
Figures 2 and 3 show examples of bull's heads mounted on re-constructed harps from Ur, which are now in the British Museum. In figure 2 the bull's head is made of gold with the beard made of Lapis Lazuli, as is the beard on the harp in figure 3.
When Leonard Wooley excavated the harps at Ur, he was unable to preserve the wood, but he was able to make plaster casts of the harps as they remained in the ground and these casts were used to re-construct the wooden portions of the harps. Note the "tuning pegs" at the top of the harp in figure 3.