What is us the difference between Bach and Beethoven's music?

Bach wrote primarily for the pipe organ in his church, and his music has a distinctive cadence regularity to it. Beethoven wrote for symphony orchestras (and smaller ensembles), and although all music has rhythm, you are much more likely to notice, in Beethoven's music, a theme that seems to jump about within the orchestra from instrument to instrument, as it varies, evolves, and returns to it's initial simplicity. Perhaps the clearest example would be Beethoven's 5th. Good luck on your exam. Make some time to track down Bach's Toccata and Fugue for Organ in D Minor, put on some good headphones, and turn up the volume.