Basic Theory: The Jig
In the example below, notice the fact that there are only two beat groupings per bar--contained within the brackets under the staff. Each of these beats is equal to a dotted quarter note (or three eighth notes). Notice the arrows and numbers showing where each beat starts.
In 9/8 time, commonly called a "Slip Jig", dividing the top number by three gives you 3 beats per bar. Those three note groupings are clearly visible in the example below.
"Jig-gy". Drum corps with little or no "jig experience" should learn jigs containing these four rhythms exclusively.