# AU Does Not Pass MIDI Within Blue Cat Audio Patchwork

**URL:** <https://forum.scalermusic.com/t/au-does-not-pass-midi-within-blue-cat-audio-patchwork/13360>\
**Category:** Bug Reports\
**Tags:** StudioOne, Mac\
**Created:** [April 9, 2023, 9:57am UTC](https://forum.scalermusic.com/t/au-does-not-pass-midi-within-blue-cat-audio-patchwork/13360 "2023-04-09T09:57:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dcarmich](https://avatars.discourse-cdn.com/v4/letter/d/f0a364/32.png) [@dcarmich](https://forum.scalermusic.com/u/dcarmich)\
**Post date:** [April 9, 2023, 9:57am UTC](https://forum.scalermusic.com/t/au-does-not-pass-midi-within-blue-cat-audio-patchwork/13360/1 "2023-04-09T09:57:05Z")

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When I instantiate Scaler 2.73 within Blue Cat Audio Patchwork (to enable the use of multiple instances of Scaler within Studio One 6), I am not able to pass MIDI to other VST/AUs within the same Patchwork instance. However, when I instantiate the VST3 equivalent, it passes MIDI successfully.

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**Author:** ![jamieh](https://yyz2.discourse-cdn.com/flex012/user_avatar/forum.scalermusic.com/jamieh/32/1139_2.png) [@jamieh](https://forum.scalermusic.com/u/jamieh)\
**Post date:** [April 9, 2023, 4:07pm UTC](https://forum.scalermusic.com/t/au-does-not-pass-midi-within-blue-cat-audio-patchwork/13360/2 "2023-04-09T16:07:03Z")

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The AU spec does not allow for MIDI to be passed. That is why VST and VST3 are really the ones to use.  
This is a problem with the AU spec and NOT Scaler. Until Apple decides to rectify this, use VST or VST3 versions.