I have GarageBand on both my iPad Air and iPhone 6 (iOS 9.2.1, GarageBand 2.1). I have experienced this problem on both platforms.

I have put many hours recording guitar and bass on relatively small projects (max 10 tracks, about 1 minute). I experienced the "Optimizing Performance" message some times, that lasts for about 5-10 seconds. When I saw this, I thought it was okay; it was caching and/or preprocessing stuff to accelerate 'live' playback. I would accept that.

However, I noticed that the playback sound quality degraded after this. By degradation, I mean the following. I record many high-pitched rock guitar parts with enough gain to have a 'rock' distortion, so the signals have a fair amount of high frequencies. After the "Optimizing Performance" degradation, the high frequencies distorted to be painful to the ears. I am not an expert, but my guess is that the "Optimizing Performance" is in fact a 'downsampling' or a 'compression' of the signals.

Again, I would accept that, if it was only for the 'live playback'; when exporting the project to a sound file (*.m4a), I would expect GarageBand to take the original full bandwidth good quality signals that I recorded in the first place. However, it does not; the resulting exported songs' quality is still bad.

So, my conclusion (that I turned into a question to this community for a confirmation) is that this "Optimizing Performance" is a downsampling/compression of the signals in an 'irreversible' way, which is a pretty way to say that it is ruining everything (by everything, I mean a lot of time and efforts). Again (I am a good guy), that would be okay, but if at least I could be warned that this might soon happen, so that I can clean up my project to release memory. For now it just explodes in my face and I cry.

Anyone else experienced a degradation from the "Optimizing Performance"? Is it really an irreversible downsampling/compression of the signals? Is there a way to block or at least revert this to get back the original signals when it happens?

I have to say that I did not test the 'undo' option; each time it happened, I freaked out and closed/opened back GarageBand (it clears any possible undo). This was panic acting. But still, I would like to hear anyone's experience on this.


Apple is pretty mum on what "Optimizing performance" means, so we only have speculation to go by, but I have noticed a few things and have an idea for you. I have noticed that turning off all reverb and delay effects causes it to happen much less frequently. This would indicate it's some sort of preprocessing or pre-generation to save CPU cycles on playback. The fact that I currently have a 40-minute piece in iOS GarageBand that is taking up 6GB on disk, even though the piece is almost entirely midi tracks and contains no live instrument or vocal tracks, would corroborate that it is storing audio tracks. This is also corroborated by the fact that if I change the tempo, it reliably immediately does an "Optimizing Performance" the very next time I try to play it.

Remember, GarageBand is much more processor-intensive than ordinary audio, because instead of just a left and right channel, it has individual left-and-right channels for every track, which must individually be panned, processed with reverb/delay, etc. So it's entirely possible that it's generating much lower-bandwidth lossy-compression versions of your audio for playback within Mobile GarageBand just to reduce processor load while multiple tracks are playing.

However, based solely on long experience, I would conjecture that it does not reduce the quality of your original audio, but rather, generates a second "optimized" file for use just within the program during playback. I bet if you were to export the entire project to an audio file, your original guitar sound wound be there in sparkling full fidelity.

If you wanted to test this out and report the results back here, I bet you'd be doing a service to the community and the odd Googler who finds this while hunting down the same question.

Obviously, if I'm right about that, it would mean iOS GarageBand is not an ideal app to do final mixes on, since you can't actually hear what it will really sound like until you export the results. Hmmm... An Apple app that includes a fundamental shortcoming which makes it a less-than-ideal tool for a serious user who wants it to do what they're advertising it for... Could that even be possible? Hmmmm.

  • Thanks for your response. "I bet if you were to export the entire project to an audio file, your original guitar sound wound be there in sparkling full fidelity", that is what I thought too, but exporting the project to a sound file (*.m4a), I still get the compressed signal versions. Original signals should be there, somewhere... or maybe not. Maybe, on iOS, memory constraints were important enough to motivate this quality sacrifice, hoping that in most cases it should be negligeable.
    – jnthngdbt
    Jun 1 '16 at 16:22
  • Darn. Yeah, GarageBand on iOS is such a mixed bag. Love having a semblance of GB on iOS, but the drawbacks and cut corners can be really frustrating. Jul 20 '16 at 14:48

I may have a workaround to get to export the song without the degradated signals caused by the "Optimizing Performance" process, but it implies having 2 iOS devices.

On iOS device #1, record, mix and have fun. If the "Optimizing Performance" happens, leading to a degradation of signals, let it be, even if frustrating. When ready to export the song, on iOs device #1, exit the song and let it update to iCloud. At this point, in my experience, if you export the song via iOS device #1, it will contain the degradated signals.

On iOS device #2, open GarageBand and wait until the song is updated via iCloud. Do not open the song, otherwise the "Optimizing Performance" process may happen and you will have degradated signals on iOS device #2 as well. Without opening it, export the song. It will have a good quality.

So, this at least answers one aspect of the original question: the “Optimizing Performance” operation does NOT induce an irreversible degradation of recorded signals.

However, the question to how to easily get back the original signals to export the song in good quality within a single instance of GarageBand is still open.


That happens to me, but then I just move the bass knob on the track settings and fix for that track.


Yeah under plug ins and eq moving the treble and bass back and forth a bit does bring back the same quality. Make sure optimise performance doesn't reformat anything before moving your track off garage band for Download or upload.


I am a producer and rapper and I have had the exact same problem. I have one solution:

Constantly make copies of your song until it is finished. Everything you change in your song, make sure you make a copy of the song so you don’t lose your work.

When it randomly says optimizing performance and it ruins your whole song, press select all and copy your whole song. Close your song and open one of the other songs you saved as a copy. Delete the whole song and paste the first one you copied. After that there should be no distortion.

Or you can just keep making copies all the way through so if you have that problem just click another song that is copied and will be the exact same.

It’s a pain though because every time it says optimizing performance you have to do it. I always make sure I have 3 copies of my completed song in case that stupid glitch happens.

I am currently producing my best instrumental and this problem keeps happening, that is why I wrote this answer to help.


Double click on the blank space and choose "select all" by. With all regions of all tracks selected, double click any track and click "settings", then "reset all". I thought I had lost hours of work but this cleared up the distortion for me.

Note: Keep in mind this will remove all quantization, looping, and quantization.

  • 1
    That seems like a promising answer, but I can't find the "reset all". I double-clicked on a region without any track, and chose "select all", so that all my tracks were selected. Then, in this state, I went in the "settings" at the top right of the screen (and tried pretty much everywhere else), but I can't find any "reset all". On what version of iOs Garage Band are you? I'm on version 2.1.1 (4369.14), on an iPhone 6 (also on an iPad Air). Thanks.
    – jnthngdbt
    Jun 16 '16 at 16:19

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