Durrty Dubbles works on double beats using variations that allow for one hand to check the timing and sound quality of the other hand. You must variously create doublestop doublestrokes, doublestrokes where the first note of one hand coincides with the second note of the other, and singlestroke fours. The unison doublestrokes facilitate building a completely uniform doublestroke motion between the two hands. The half-unison doublestrokes force you to match sound quality and timing when the doublestop note is achieved through differing amounts of forearm assistance, wrist turn, and fulcrum pressure between the two hands. The single-stroke fours give you an opportunity to hear each note of both hands’ doublestrokes by itself, without being hidden within a doublestop.