remuslives23.livejournal.comI read this not long ago but forgot to bookmark it. Blaine and Kurt wrote a song/performed a song that was chosen for the New Directions to sing at Regionals/Sectionals. But it was decided that Rachel and Blaine (I think) should sing it instead as they thought it would go down better with the judges.
Once at the competition, the Glee Club watch the other groups perform and see two boys singing a duet together. Afterwards, those boys approach the Glee club and are surprised when they find out that the New Directions hadn't allowed Kurt and Blaine to sing together.
There is a similar fic on ff.net but it ends before the competition performance and is not the one I'm thinking about.
Thanks for any help you can offer for my first search. :)