Apropos of nothing, except the fact that I watched the movie again recently: the best bit in the movie Shoot the Piano Player is Truffaut's gimmick of flashing the lyrics on the screen as Boby LaPointe sings his song "Framboise."
There is, or was, a story that Truffaut came up with the idea because he couldn't hear what LaPointe was singing and feared that the audience wouldn't either. The sound recording is indeed a little odd and sometimes indistinct in this song, and strangely enough it appears to be one of the few parts of the movie that uses direct sound, since almost all the dialogue was post-synchronized. If so, it's an exact reversal of the way things are usually done: usually musical numbers are post-synched and dialogue recorded directly.
I also like the joke -- even if it wasn't intentionally done as a joke -- of having a famous singer, Charles Aznavour, and keeping him in the background at the piano while a long song is sung by someone most of the audience hasn't heard of. It's sort of the more exalted predecessor of the movie Tony Rome where Frank Sinatra is the star, but the only person singing in the movie is his daughter Nancy.
(Note: I am not comparing Shoot the Piano Player, a terrific movie, to Tony Rome, a movie shot so Frank Sinatra could get a trip to Florida. I'm just saying that they, and other movies, play a basic joke on the audience by casting a singer and then giving the singing to somebody else.)