changing speed of mp3's

Hai
do you know of software that can slow down or speed up mp3's (or wav-files). Important: i want the pitch to change accordingly when i speed up or slow down the track (just like with an old-fashioned tape-recorder).
I want to use this software for 'repairing' digital files that were recorded directly from tape-recorders.
There is abundant software that can change either the tempo or the pitch of a digital file, but i have not encountered a product which can do that simultanously.