A quick guide on how to permanently ''correct'' the audio:
avidemux and audacity are free and portable, you may need to set ffmpeg in audacity to import aac.
1 - avidemux >audio > save audio
2 - audacity > select all > effects > change pitch (use the slider) > export as wav
3 - avidemux > audio > select track > click on track 0 (original) > add audio track > select the edited wav
4 - set audio output to aac (fdk) > save video
I'm not sure of the exact amount of pitch, from -1 to -30, videos with background music are good to use as a base.
If anyone knows the exact value, please comment or pm me.