Songs for dating
The Swell Season was released in August 2006, and The Cost in February 2007, before the release of Once.
However, the AMPAS music committee determined that, in the course of the film's protracted production, the composers had "played the song in some venues that were deemed inconsequential enough to not change the song's eligibility".
It was written by Uruguayan composer Jorge Drexler, but the producers would not let Drexler perform the song during the show for fear of losing ratings.
Instead, the song was performed by Carlos Santana and Antonio Banderas.
The number of nominations is now contingent upon the number of submissions.
When neither of those is able to do so (or in rare cases where the telecast producers decide to go with someone else), the Academy chooses more well-known entertainers to perform the song at the ceremony.
For example, Robin Williams performed "Blame Canada" from South Park: Bigger, Longer & Uncut at the 72nd Academy Awards instead of the film's voice actors, Trey Parker and Mary Kay Bergman (Bergman died a few months before the show).
There was a debate as to whether or not Glen Hansard and Marketa Irglova, who were awarded the Oscar in 2008 for "Falling Slowly", were in fact eligible.
"Falling Slowly" had been released on two other albums – The Swell Season, Hansard and Irglova's duo project, and The Cost, by Hansard's band The Frames.