I barely got the wrapper off my new copies of GPO and JABB when an application came along. Unfortunately I can't provide a link or sample, due to the REAL "First Law of Copyright" -- to wit, Don't Mess with the Mouse!
Working sound for a production of Disney's "High School Musical," with a junior high cast. The Disney-supplied backing tracks are complex and interesting, but they all but go out of their way to avoid giving the poor singer any hint of their pitch.
In deperation, and with full consultation with the vocal director, I started up GPO (and a few other samples I had lying around) and doubled the vocal lines in a couple of key places. An hour or two of tweaking, and the new material is all but invisible (except to someone very familiar with the original backing tracks).
Maybe not the most original composing job to have. But exciting to know that we can put the option a real pit orchestra gave us back into the hands of a vocal director -- even when we are stuck with pre-recorded material.