"he who pays the piper calls the tune"

A wandering minstrel playing the pipe and tabor
Public DomainA wandering minstrel playing the pipe and tabor - Credit: W.F.Dawson
This proverb dates to the old English tradition of music provided at country fairs, on village greens and other social occasions (spontaneous or planned) being provided by wandering musicians – usually pipers or fiddlers. Quite simply, the person paying for the musician’s services had the right to command their repertoire, and the proverb passed into common language to mean that the person doing the paying in any given situation is also the person in charge of the decisions.