From Season 3's episode "Martin Does It His Way": Years ago, Martin had composed a song, hoping that Frank Sinatra would someday sing it, but Martin had forgotten all about it. With Frasier & Niles' help, they complete the song, and send it in to Sinatra's people, with the hopes that it would be accepted and recorded.
Brothers and Martin working on song Martin wrote for Frank Sinatra, “Groovy Lady”
http://www.youtube.com/watch?v=VbMwyT2RjEEAt the same time, Frasier's & Niles' great aunt dies, and according to the aunts' wishes, Frasier was chosen to deliver the eulogy. Reluctantly, Frasier tries to compose a eulogy, but has difficulty due to the aunt not being well-liked by the family. Martin finds out that his song was not accepted. Frasier, however, has other plans for the use of the song, as you see here in this clip
“Groovy Lady” by Frazier and choir
http://www.youtube.com/watch?v=_wmAwimQXOM