Midi devices and software. I know a few musicians who use midi stuff. Basically keypads with a diskette drive and an LCD screen. There are midi keyboards, and drum pads, and a lot of other stuff too... There are progs available for making midis the HARD way, but they're hard to come by. Ages ago on Tech TV or something, I saw a segment with a prog that could pick notes up via microphone and convert them to an editable format. You could whistle or hum a tune into it. Very handy for those of us not lucky enough to have been taught how to play the piano.
Actually MIDI isn't that hard to use. There's software like Finale which let's you type in sheet music, and convert them to MIDI. Granted the program is a bit expensive, but if you goto a school where they have a decent Music dept. then you should be able to get a hold of it and use it. Also you can use a simple MIDI cord and hook a keyboard, and other instrumetns to your computer. You don't need a diskette equiped keyboard. It's a bit tricky at first, but once you figure out the software, it can be alot of fun. Also I think you can get programs which can convert and .WAV file to MIDI, but don't hold me up to that.
No, there is no software for converting WAV audio to Midi - they are completely differnt things (like converting a vehicle into a television). Midi stands for Musical Instrument Digital Interface is is really just a standard for recording the length, pitch and velocity of notes, usually played on some kind of Midi compatable instrument. The computer then interprets this data and matches the note information with prerecorded sounds (usually stored in your sound card).
WAV data, on the other hand, actually records the sound of an instrument (or whatever).
There are plenty of tools out there for creating Midi music. At the moment I use Cubasis AV which I got free of some magazine. Cubasis lets you create music by editing music scores (like Finale, mentioned by gofamon), with a keyboard (or other Midi instrument) or by way of drawing notes onto an on-screen keyboard.
See if you can find someone with sibelius, its expensive musicians software but you can scan sheet music into it with a scanner, and after tinkering with it to make sure it did it right you can save as a general midi file, one of my friends is a composer and has it
There is a program to convert wav to midi. Problem is it doesn't do it well at all. It examines the wav file and tries to match it with midi but it comes out sounding almost nothing like a recognizable tune.
EDIT: On closer examination, those wav to midi programs will work best on single instrument wav files. I guess they work on the same principles as those expensive-as-#### guitar to midi converter doodads.