Use a program like Musicmatch Jukebox to convert mp3s to wave files, change the keys of wave files with Keyrite, and using the same Musicmatch Jukebox , convert the files back to mp3s. Basic free versions of Musicmatch Jukebox are available.
I don't know of any software that will change the keys of music files faster than keyrite. I mentioned Goldwave. (free downloads are available) It will do two different kinds of key changes. One that goes pretty fast, but there is a corresponding tempo change (pretty handy if that's what you need) But,
To not change tempo, my computer 600 megahertz, will do a short song using Goldwave in about 30 minutes! I don't know your situation but it will still be probably two slow. Goldwave will do file converting as well if you follow the instructions and get the right plug-ins
I really suggest you just convert files and then use keyrite. I hope you find what you need and your contests go well.
PS. I know what it is like not to be able to get on the Forums after a certain amount of time. Don't worry and sorry if you felt under pressure. We're just anxious to help.
