iPhone and iPod Touch have a useful (some would call it 'insanely great')
feature to be able to playback audio files on 2x and 1/2 speed,
with same 'pitch' of the voice, just faster of slower.
Some other mp3 players can speed up, but sound gets distorted,
sounds like chipmunk or Donald Duck.
As usual with Apple products, this feature works as 'auto-magic'
based on metadata ('info') of the file,
so mp3 files need to have a flag that is a podcast or audio book.
This is not always the case for mp3 files, and iTunes can help.
forum @SuperUser
...to get my mp3 lectures to play at double speed on iPhone (and iPod Touch)
iTunes uses to tell whether the file is a podcast or audiobook is a setting in:
"File-> Get Info-> Options tab-> Media Kind"
Set that to podcast or audiobook and voila,
iPhone will give you the option of 2x speed.
This is great, because you can select a bunch of tracks
and change the whole lot with a few clicks.
Microsoft has also added similar feature to Silverlight 5,
that is for now only available on 'standard' Windows,
not not yet on Windows Phone 7.x.
Too bad that Internet Explorer 10 on Windows 8 'Metro' interface
will not support plugins, including Silverlight...
