It is common to package an extra disc of material with some Releases. These are labelled with the DiscNumberStyle.
- "Mother Nature Calls (bonus disc)"
- "Greatest Hits (bonus disc: Acoustic Hits)"
A Bonus Disc is a disc of material that is consider extra to the Release. It is used to show the difference between true multi-disc releases (eg, The Beatles - The White Album (disc 1) & (disc 2)), and normal releases augmented by bonus tracks (eg, The Fall - Hex Enduction Hour & (bonus disc)).
Note that the presense of bonus tracks on the primary disc of a release does not mean any subsequent discs aren't Bonus Discs. A distinction is always made between true multi-disc releases and bonus discs.
Also note that the ReleaseAttribute for a Bonus Disc will normally not be 'album', unlike the primary release.
(this proposal will probably need to be in DiscNumberStyle as well/instead)
Discussion On Ammendment
One thing I'm not entirely sure about is how to handle expanded releases which have had their titles changed. Eg, Tri Repetae was also released as Tri Repetae++ 1) & (disc 2). I think we should represent the "++" despite the fact it seemingly only indicates the presense of the bonus disc. I propose renaming the discs to Tri Repetae++ and Tri Repetae++ (bonus disc) respectively. However since things like "Special Edition" are dropped, perhaps we should drop these too? --Gecks