>> Are you sure you mean "proprietary" and not just "internal"? Sorry to pick
>> nits, but if you meant exactly what I think you said, I'm confused.
>
> It is the internal format, but not "just". Audacity converts all audio to
> it's own .aup format at load, which is also the only format it is possible
> to save in. (.wav, .mp3, and .ogg are EXPORT formats.) As far as I am
> aware, only Audacity is able to read that format, making it proprietary.
I think 'proprietary' implies that it would be *illegal* to write
another program that can also read .aup files. Given that Audacity is
GPL'd, it seem more likely that someone *could* write such a program,
but no one has bothered to yet.