I saw a documentary on the making of Sgt Pepper once. In an interview with George Martin, he said he'd given the half-orchestra the instruction that they had to have played their lowest and highest note, and that he'd written them little signposts to let them know where they were. It didn't matter how quickly they got to the highest note they each could play, but they had to have done that by the time that section was over.
Paul apparently found it funny that certain sections of the orchestra had a herd-like mentality. The violins would all invariably follow each other and go up together, while the trumpets (who, according to Paul are always "well-oiled") were rather more carefree!
