As I once played the piper I must now pay the count

Phrase: 'He who pays the piper calls the tune' meaning that the person who provides the money for something can decide how it should be done.

'The Pied Piper of Hamelin' is a folk tale, among others written down by the Brothers Grimm. It tells about a disaster in the town of Hamelin, Germany, that supposedly occurred on June 26, 1284. In that year a man came to Hamelin claiming to be a rat-catcher. The people of Hamelin promised him payment for killing the rats. So the man took a pipe, attracted the rats by his music and made them follow him to the Weser river, where they all drowned. Despite this success the people reneged on their promise and did not pay the rat-catcher. http://en.wikipedia.org/wiki/The_Pied_Piper