Do you know a program to change the speed of audio files?

Question

Sound processing

I can't find a suitable program for Windows that would be able to:
• Speed ​​up the tempo of mp3 files (up to x2 speed; keeping the key, of course)
• Do volume normalization
• Save in mono (to fix recordings that hit in one ear)
• Process files in batches (so that you can feed the entire audiobook at once)
Do not offer player applications for smartphones, I need ready-made files for an old player.
If you know such an audio editor, please share the name.

Answer 1

Batch Processing in Audacity