five-finger exercise

noun2

1. •
   A musical composition for the piano, designed to require the use of all the fingers of the hand for the purpose of skill development.
2. •
   (figurative) An activity which is undertaken for the purpose of skill development.

   • Batman Begins, the 2005 film that launched Nolan's series, was a mere five-finger exercise. This is the full symphony. — 2008