In the Wintel World lots of computers came with ROM drives that are hardware-incapable of reading either multisession or active audio disks. Others are capable of active audio reads but not multisession. Roughly the same proportion are vice-versa incapable. In the Apple World things are much better. We have provided a Tech Checklist to step though the process of determining what's what in your life.
Later pressings are multisession.
For an explanation you need to go elsewhere. This page is an ongoing experiment in providing technical support over the Web and is updated as we learn more. If you see that some of our information is out of date or wrong or needs supplementing please contact us. If you encountered problems and solved them yourself, help us help others by telling us about it using the Solutions Feedback Form . This is the place to start.