The Bar Percussion Solo Notebook by Pimentel has several class 3 four-mallet solos that I find really helpful in getting my kids to learn 4-mallet technique. The very first one in the book, "What Shall We Do With the Drunken Sailor," for example, is a 5th in both hands with the only lateral motion within the 5th. Halfway through the melody switches from the right to the left hand, so both hands get practice being the focus hand.