Wooster at the piano is trying unsuccessfully to match the words with the notes of Irving Berlin's "Puttin' on the Ritz" (1929). Jeeves offers his trademarked advice, this time telling Bertie that "it seems to be a reasonably straightforward syncopated 5/4 time signature." It is, indeed, syncopated - more than almost any other song of its time - but it is in 4/4 time throughout.
In the Hotsy Totsy club, Bertie and Honoria are dancing to a band, the music played on the soundtrack features a muted trumpet playing the melody, alas the trumpet on the stage has no mute inserted.