Ratios refer to the relationship between the rhythm of the song and the rhythm that is being superimposed on that. For example, let’s say you have a 4/4 measure. One rhythmic layer uses the 4-beats reference for that measure, and the second divides the same 4/4 measure into 3 beats. This is referred to as a 3 against 4 or 3:4 polyrhythm.