AU

From DNBWiki

AU stands for Audio Unit. Audio unit is a Macintosh specific audio plug in format similar in principle to VST plugins.

[edit] History

When Logic moved from the Mac OS 9 (also refered to as classic) to the OS X operating system, it ceased to support VST plugins in favour of the macintosh only Audio Unit plugin format. This was possibly a way of becoming free of the Steinberg VST plugin system and of creating a plugin format that would be optimised for the Logic and Mac OS X platform. At about the same time, Logic had been purchased by Apple from the German company Emagic and the decision to not support the VST standard can probably be related to Apple's decision to discontinue support for Logic on the Microsoft Windows operating system. Apple probably hoped to sell more Macintoshes by making the popular industry standard Logic sequencer Macintosh only. The Last version of Logic released for the PC: Logic 5.5 is still a widely used and highly functional sequencer despite being discontinued and therefore impossible to purchase.