Apple Logic Express 9 - Manual (Page 773)

2 Within the instrument interface, you need to set up the output routing for individual
sounds or samples. This is generally done using a menu with entries such as Main, 34,
56, and so on.
3 In the Mixer, click the Add (+) button of the instrument channel strip that you have
inserted the multi-output instrument in—such as Ultrabeat.
Note: The Add button (+) appears only on multi-output instrument channel strips.
773 Chapter 27 Mixing