As a king one was obliged to perform a number of duties, including recieving various guest of high and low, oftentimes in designated audience rooms. These rooms were not necessarily the same from one king to another since many danish kings needed to keep up with the fashion of their time, either by building entirely new palaces or simply by refurbishing rooms in the already existing palaces. As time went on it became increasingly important to separate and recieve guests according to their rank, in order to maintain a certain degree of social hierarchy.
The Winter Room was widely used by Christian IV as an audience room, making this peephole a particularly clever contraption – this enabled him to prepare for the next guests. Alledgedly also used to impress visitors – by waving his hat he would be discreetly signaling to one of his servants looking through the peephole, to instruct the hidden musicians to start playing.