In the synchronous scheme, there are no odd-valued throw heights. If the scheme is synchronous, a pattern could be 2-fold mirror symmetric. However, there are two kinds of each even-valued throw, those that cross, and those that don't, the former denoted by an x after the number. These 6xs are always on one side. Note the 4s alternate sides.
Multiplexing occurs when more than one ball is in a hand at a time.
Then, with multiple balls being thrown during any given beat, the throw heights are given for each of the throws made. The convention is for square brackets to denote the different throws made by each hand. They both deplete the pattern, and then suddenly give it all back in a burst of balls. Computer programs exist to furnish valid tricks under any scheme of rules. Siteswaps make up a doubly-infinite family of tricks.