<s>
Audio	B-Operating_System
Units	I-Operating_System
(	O
AU	O
)	O
are	O
a	O
system-level	O
plug-in	B-Application
architecture	O
provided	O
by	O
Core	B-Operating_System
Audio	I-Operating_System
in	O
Apple	O
's	O
macOS	B-Application
and	O
iOS	B-Application
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Audio	B-Operating_System
Units	I-Operating_System
are	O
a	O
set	O
of	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
services	O
provided	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
to	O
generate	O
,	O
process	O
,	O
receive	O
,	O
or	O
otherwise	O
manipulate	O
streams	O
of	O
audio	O
in	O
near-real-time	O
with	O
minimal	O
latency	O
.	O
</s>
<s>
It	O
may	O
be	O
thought	O
of	O
as	O
Apple	O
's	O
architectural	O
equivalent	O
to	O
another	O
popular	O
plug-in	B-Application
format	O
,	O
Steinberg	O
's	O
Virtual	B-Application
Studio	I-Application
Technology	I-Application
(	O
VST	B-Application
)	O
.	O
</s>
<s>
Because	O
of	O
the	O
many	O
similarities	O
between	O
Audio	B-Operating_System
Units	I-Operating_System
and	O
VST	B-Application
,	O
several	O
commercial	O
and	O
free	O
wrapping	O
technologies	O
are	O
available	O
(	O
e.g.	O
</s>
<s>
Celemony	O
Software	O
and	O
PreSonus	O
have	O
also	O
developed	O
the	O
Audio	B-Architecture
Random	I-Architecture
Access	I-Architecture
(	O
ARA	O
)	O
extension	O
,	O
which	O
works	O
for	O
both	O
AU	O
and	O
VST	B-Application
,	O
allowing	O
greater	O
integration	O
between	O
the	O
plug-ins	B-Application
and	O
DAW	B-General_Concept
software	O
.	O
</s>
<s>
Audio	B-Operating_System
Units	I-Operating_System
allows	O
sound	O
file	O
audio	O
time	O
stretching	O
and	O
pitch	O
scaling	O
(	O
e.g.	O
,	O
timestretch	O
)	O
,	O
sample	O
rate	O
conversion	O
,	O
and	O
streaming	O
over	O
a	O
Local	B-General_Concept
Area	I-General_Concept
Network	I-General_Concept
.	O
</s>
<s>
It	O
also	O
comes	O
with	O
a	O
set	O
of	O
AU	O
plug-ins	B-Application
such	O
as	O
EQ	O
filters	O
,	O
dynamic	O
processors	O
,	O
delay	O
,	O
reverb	O
,	O
and	O
a	O
Soundbank	O
Synthesizer	O
Instrument	O
.	O
</s>
<s>
AU	O
are	O
used	O
by	O
Apple	O
applications	O
such	O
as	O
GarageBand	B-Application
,	O
Soundtrack	B-Operating_System
Pro	I-Operating_System
,	O
Logic	B-Operating_System
Express	I-Operating_System
,	O
Logic	B-Application
Pro	I-Application
,	O
Logic	B-Application
Pro	I-Application
X	O
,	O
Final	B-Application
Cut	I-Application
Pro	I-Application
,	O
MainStage	B-Application
and	O
most	O
3rd	O
party	O
audio	O
software	O
developed	O
for	O
macOS	B-Application
such	O
as	O
Ableton	B-Language
Live	I-Language
,	O
Amadeus	O
Pro	O
,	O
Ardour	B-Language
,	O
Audio	O
Hijack	O
,	O
DaVinci	B-Language
Resolve	I-Language
,	O
Digital	B-Operating_System
Performer	I-Operating_System
,	O
Gig	B-Operating_System
Performer	I-Operating_System
,	O
REAPER	B-Application
,	O
and	O
Studio	B-Application
One	I-Application
.	O
</s>
