I recently heard about scientific pitch and Verdi A pitch which uses a 432 Hz instead of 440 Hz that the ISO decided on. I know about Larouche already. I wanted to try 432 anyway, so I wrote a macro today to convert my MP3 files. The online help suggests to not exceed 500 files at a time when you use this macro. You can save this to a text file then import this macro and use the Files button to select which MP3s to convert. The output goes to the Documents\Audacity\macro-output\ folder on my system.