This is an aspect of monetary policy which was already stressed by Shackle in his 1949 article on “The nature of interest rates.” Describing a situation in which the central bank tries to bring interest rates down he states that [p. 115] “a consensus of market opinion can be swung, by words and deeds of the monetary authority or its masters”.
The structure of the basic New-Keynesian model can be easily represented by three equations characterising the dynamics of the interest rate, output and inflation. The first equation can be related to the supply side, the second to aggregate demand, and the third specifies monetary policy behaviour.