Here are two ways to count the thirty-seconds. No. 1 is as a straight 8 count. This works well at slow tempos and ensures your accuracy. At faster tempos it's not so good. No. 2 shows the relationship of thirty-seconds to sixteenths. This is how I would count the thirty-seconds only after making sure that I have the figure down.
In the Polyrhythms and Rhythm Clusters area near the end of the exercises you will notice the use of brackets that would normally be used on odd numbered groupings. Why you might ask? It makes it much easier to read the rhythms in a group when there are lots of figures with broken up thirty-second rests next to each other.
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Hear the exercises played at 40 bpm. Time: 38:54