Here you can learn where to get midi sheet music downloads on the web
MIDI is a technology that represents music only in digital form. Unlike other digital music technologies such as MP3 and CDs, MIDI messages contain individual instructions for playing each individual note of each individual instrument. So with MIDI it is actually possible to change just only one note in a song, or to orchestrate and entire song with entirely different instruments. And since each instrument in a MIDI performance is separate from the rest, its easy to «solo» (listen to just one) individual instruments and study them for educational purposes, or to mute individual instruments in a song so that you can perform that part yourself.
Most film and TV scores, as well as much popular recorded music is written and performed using electronic keyboards and other MIDI-equipped musical instruments. (Thanks to advances in digital sampling and synthesis technologies, the orchestra playing behind that big-screen block buster is more likely to be the product of MIDI than a real orchestra with dozens of acoustic instruments.)