Orphaned Series/Music

Examples of Orphaned Series in Music include:

The Vocaloid series "Synchronicity" was thought by fans to have been abandoned, since the third and final video in the trilogy has yet to be released. This notion was perpetuated when an incomplete version of the final video was allegedly posted on Japanese video sharing site Nico Nico Douga before quickly being removed. However, the creator of the series, Hitoshizuku, claimed that no such video was ever uploaded, and she has confirmed on her blog that the conclusion to the series is in progress, though she stated that fans might have to way awhile for it to be released.
The 1995 David Bowie album 1. Outside was intended to be the first part of a trilogy of concept albums. Bowie apparently lost interest in the project.