Lack of a Mod Wheel can be difficult since the Mod Wheel controls volume in Personal Orchestra. The on screen mod wheel in the Kontakt Player can be used with the mouse to set an overall volume in standalone mode. Users of notation programs and some sequencer users can "draw" controller data with a mouse into their programs. And most sequencers allow you to reassign controllers, say, from the Mod Wheel to another controller.

Some GPO users have devised a workaround for Cubase/Nuendo, and Sonar users and have written Sonar and MFX plug-ins that reassign the Mod Wheel to a pitch wheel or other controller. See the 'User Created Programs' section of the Downloads page for these plug-ins.

(from garritan.com)