Pay the piper/fiddler
The complete expression is ‘he who pays the piper calls the tune’ meaning that whoever puts up the money has the right to control events and is first cited in English in 1638. It is often claimed that the expression derives from the 14th century German legend of the Pied Piper of Hamelin who was contracted to get rid of the town’s infestation of rats. When the town folk refused to ‘pay the piper’, he led the town’s children to their doom. Although the Pied Piper legend first appeared in English in 1605, it was in a little-known work by Richard Verstegan, alias Richard Rowlands, and was not widely known to the public until Robert Browning’s version of the legend appeared in poetic form in 1842. It is highly unlikely, therefore, the Pied Piper had anything to do with the origin of the expression. From the Middle Ages, British people had been enjoying the music of travelling pipers and fiddlers, so paying the piper and having the right to choose what he played must have been going on for a long time before the expression became figurative in the early 1600s.