I have an MP3 that starts slow and speeds up as the song progresses. Is there a way to control the timing so the whole song is the same timing?
There may be no practical way to fix that. You might be able to make 10 small speed changes, or something like that. If you try that, make sure to start/stop each selection on a zero-crossing do you don’t get a glitch in the middle of a wave.
Or, you might be able to find a plug-in that accelerates & decelerates the speed. But finding the right acceleration/deceleration would be very difficult.
There is a program called [u]Capstan[/u] that could probably do it but it costs $200 to rent the application for 5 days!
You could try using a “Time Track” (see: http://manual.audacityteam.org/man/time_tracks.html)