how do you change the music file .wav to .midi?

Answer 1

Typing in "wav to midi converter" on your favorite search engine,
Like Google, or since we are looking for software download.com is also a good spot. Is probably your best bet here as changing a file from wav to midi is quite the process, because midi stores music data in a totally different method then wav or mp3 or other common audio format.

The main problem here is with wav, mp3 (and the like) it's storing the sound directly. a microphone picks up the vibrations that are sound translates it into bits via the sound card and those bits are written to a file. The main between wave, mp3, wma and the others is how they compress the bits to save room.

But MIDI is much different it stands for Musical Instrument Digital Interface. now as you can tell by the from the full version of the name this format was designed mainly to connect various Musical instruments together, (such as musical keyboards) and they storing what the music sounds like it stores what Instrument played what note at what time for how long.

now as anyone who compares mp3's to midi notices the MIDI's are indeed a lot smaller, this because of the difference in resolution needed Midi's still sound good only recording what's going on every second. Whereas when you’re recoding the sound directly what you’re doing is telling the speaker when to vibrate, so to make it sound smooth you got to record what's going on several times a second. This is referred to as the sample rate. 44k, which is a common sample rate, means in the space of one second it's written down what's happening 44 thousand times, now when you compare that to MIDI that at best only samples a few times a second. it means in a 3 minute song MIDI only has a couple hundred samples while the other formats are looking at several million samples. That right there is what caused the big size differnece.

Answer 2

Find a search engine..
type "wav to midi converter"
so you have more options.