It's a piece of nonsense, of course, in which the singer claims he's 'studied all the rhymes that all the lovers sing' (on the big screen) and proceeds then to give his beloved nothing but the rhymes...the rest of the song is pretty much blah, blah or, tra la la la.
It's not actually that easy a song to sing. I don't mean vocally, but just to make it work is quite difficult. I played around with it more yesterday than the previous time I sang it, but just to show how differently it can be interpreted, and how it may still not come across, check out these videos of people doing it.
First, Ann Hogan, a mezzo, performs it at a lunchtime recital in St Anne's Church, Dawson St, Dublin. The accompanist is Dearbhla Collins (which is almost an ideal name to have when accompanying this song!)
In another version, we have Eleni Pantages, accompanied by Peter Walsh.
And finally, there's the clip from the movie, Delicious, in which the song is given some context (though not much!). Russian immigrant Sascha, played by Raul Roulien, bets the Americanized Swedish valet Jansen, played by El Brendel, that he can't make up song lyrics. Roulien performs Blah, Blah, as a spoof of the pop songs of the era. This one isn't on You Tube, so you'll have to go to the link on the Turner Classic Movies site.
If you're desperate for more versions of the song, you can find a surprising number on You Tube - they vary quite a bit in quality, as you can imagine, and in interpretation...