No, I haven't been changing the content identifier because I have been treating them as a single collection (aka a book). I could construct per-chapter content identifiers, but would that cause problems in the event the chapters are just content ranges within a single audio file?

The item title is only changed when either: The current chapter has played to the end The user selects a new track in the UI directly The first case generally doesn't happen very frequently: some chapters may be a few seconds long, while others are several minutes to an hour long. The second case is driven strictly by user interaction frequency. In my tests, I follow path 2 and make a single selection and the title isn't updating.