A gat-kayda is a composition which uses the expansion rules of a kayda but uses the language of a gat. A gat-kayda utilizes the chaal or flow of a gat. It is found in gharanas such as Benares, Lucknow, and Farrukhabad . Although it is an expansionary composition, the extent to which it may be expanded is usually less than a regular kayda because the bols used in this composition are heavy bols found in gats. Another reason why we find that gat-kaydas are less expandable is because the effect of the gat-kayda primarily relies on its contrast and juxtaposition of different phrases (the phrases found in a gat are usually very diverse), meaning that it is harder to make several balanced variations connecting to the main theme. A gat-kayda uses khula baaj bols and thus can't normally be played as fast as a regular kayda.
Definition of gat: Click Here
Definition of kayda: Click Here