Program to slow down mp3 files

I am looking for someone to construct a simple program that can slow down mp3 files without changing pitch. Ideally I would like it to be able to slow down in increments, like 50%, 100% or even 200% for faster music. This software would be used for transcribing music, such as jazz solos that are difficult to hear at the normal speed. If it could be done so that you could change the key of a song without changing the tempo, that would be very cool as well, but slowing it down is my main concern. For a reference, you can check out the product at [[login to view URL]][1] ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform All widely used Windows operating systems, and Mac would be nice but not necessary.