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Serious Bus CPU Release Issue - Logic Pro X


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Made a video of the issue - I forgot to show my OS and software versions - I will list at the bottom of this post.



When audio passes through a plugin on a bus - the plugin begins to use CPU - when audio stops feeding the bus the CPU usage should drop after a few moments. _ It does not. And to compound the issue Logic does not even release the cpu until a section of the song is played without audio.

I hope there is a button or setting for this - but there doesn't seem to be.


If this users error smack me around and let me know.... I really can't solve this one.


In text form -

In my tests - the Dynamic plugin allocation - is broken in Logic - Once a plugin uses the CPU in an Aux track the program never releases it as it does with audio tracks.

I did not test with Instrument tracks. So I don't know what goes on with virtual Instruments.

I have spent a total of two days with Logic, so it very well could be user error -

but that seems unlikely - since the dynamic plugin allocation works absolutely perfectly on audio tracks.


My test was easily reproducible. So if someone could verify it is not a "just me" issue that would be ultra kind and much appreciated.


  • Set up 25 audio tracks with any audio clip on them
  • Set up 25 or more Aux tracks.
  • Set the input on all the Aux's to the same bus. Unorthodox I know - but this is only a test - If you want to later set up individual feeds per Aux.
  • Place a CPU intensive plugin across all the Aux's - So you can watch the "Performance meter" - The more plugins the better - up to about 25-90% max cpu usage make for an easy visual.
  • Audio tracks should have a send to feed the aux's input(s)
  • Play the audio watch the CPU usage and hit stop.


Now bypass the Aux's plugins and add the exact same plugins to the audio track directly and you will notice the CPU get used when audio is playing through the plugin - and when there is a gap or no audio the CPU usage drops off.


Logic seems to be treating the Aux's as audio tracks with the input monitor button selected. As if once it detects audio it does not know if more audio is on the way so it just keeps all plugins on and ready.




My specs I didn't mention in the video.

Logic Pro X 10.5.1

OS 10.14.6

2017 iMac 4.2Ghz i7

40Gb Ram


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  • 2 months later...

No I didn't. I don't really expect to see one for a while. I am still learning Logic Pro X and all of it's quirks.

I am not making a living with these programs anymore so it is not high on my "care" list.

Apple from what I can tell ( I am new with Logic) but from what I have read in these forums they don't seem to update the app all that often. "It is what it is" kind of thing. Love it or people will call you names...


But seriously Apple, not releasing the processor is a HUGE deal - and I don't understand why more users don't complain.

I see tons of posts on CPU overload and how do I fix it kind of thing. Heck my system craps out on occasion... system overload. Maybe it wouldn't of crapped out if the plugins on my aux's that no longer have audio going through them turned off.



How about fixing the dynamic plugin processing.


Or should I just start putting a single instance of reverb on every single track that needs it. I believe I tested that method and dynamic processing worked on individual tracks perfectly... go figure. But mixing like that goes against common sense. I want a few cohesive reverbs on aux returns and that is all.


And stop making aux returns that don't delete with the instrument that created them.

It is crazy how big Logic Sessions get compared to Pro Tools - it seems like the app just keep making aux's - I am always cleaning up the auto-created aux's - Maybe I don't have a good work flow because I am never sure how instruments get created - sometimes in folders - with a ton of channels and sends get made with new reverbs and choruses, distortion etc. - then If I change my mind and don't like that instrument - I trash the instrument then go through all the aux's to find which ones are orphaned.(if I remember) It is nuts that the aux returns for instruments are not in the folder stack. Then the aux's would be deleted with the stack.


But still having fun with it. ALL DAW's have issues that make you want to rip your hair out. It just depends which issues you are willing to tolerate.

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