iPad Pro bug makes music apps stutter and crackle

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IPad Pro one week review
Musicians should stick to their old iPads for now.
Photo: Andrea Nepori

If you bought the new iPad Pro for making music, then you probably already discovered that it’s almost useless for the purpose. I just hope you didn’t sell your old iPad yet. The problem, which is so widespread that it probably affects all of the new 2018 iPad Pro models, causes the CPU to spike, and sound to crackle whenever you use more than a couple of music apps together.

Fortunately, a fix is apparently on the way.

What’s happening?

Update Monday, December 10, 2018. It looks like the just-released iOS 12.1.2 beta fixes this issue. In the release notes, the fix is listed under resolved issues in Core Audio. testing will see if this is the same issue detailed here. If so, heavy audio users might want to grab the public beta when it becomes available, if they can’t wait for the official release, which may be some weeks away. 

The super-powerful new iPad Pro can handle huge, multi-layered 3-D images in Photoshop while keeping its cool. Why, then, are relatively easy-to-run music apps causing it to break?

Two instances of Moog's Model 15, and the new iPad Pro is floored.
Two instances of Moog’s Model 15, and the new iPad Pro is floored.
Photo: Cult of Mac

The problem occurs when the user runs more than a couple of music apps together. The way iPad music usually works is to have one main app that hosts other apps, in the form of plug-in Audio Units. Or, you pipe the audio and data from those apps into your main recording app, like GarageBand or AUM.

This works great, and even really old iPads can handle the load. But the new iPad chokes. To see the extent of the problem, open up AUM, which is an amazing audio-routing and recording app for iOS. It has a CPU meter in one corner, letting you know how close you are to the limit. This is important on iOS because when you max out the CPU, the sound starts to glitch and crackle (and not in a good way).

Load up a couple of synthesizer apps inside AUM, and maybe add a few effects, then take a look at the CPU meter. It’ll be up way higher than it would be on an older iPad. But you won’t need to look at that meter, because the audio is probably crackling and stuttering already.

Why can’t the new 2018 iPad Pro handle a few music apps?

It’s almost certainly a software problem. The developer of AUM contacted Apple about this problem, and — according to this report from AudioBus forum member Genshi — he received a reply from Apple:

I contacted Apple this morning shortly after replying to your email, they have confirmed an issue with this model of iPad and have told me to file an official bug report in order that I may be kept in the loop with what’s going on. It seems there is an issue in the audio system in iOS affecting this model.

The good news is that the issue has been tracked down, and a software fix is possible. An Apple engineer contacted Genshi directly with the news:

After I sent this note, I was able to track it down and it appears that an actionable related issue is with the right team and they are investigating. I will keep monitoring that.”

That was back at the end of November. Since then, iOS 12.1.1 has been released, and the fix still hasn’t been made available. According to another iOS music app developer, Bram Bos, Apple is just working out how to release it:

Apparently it has already been solved. Last thing I heard Apple was “looking for a vehicle to release the fix”.

What to do in the meantime?

The only workaround at the moment is to keep using an older device. Even when using just one or two apps, my new iPad Pro crackles and spits, making it unusable for anything other than the most basic audio production.

If I confine myself to GarageBand, without piping in any extra audio apps, I can avoid the problem. But the best bet, reliability-wise, is to revert to your previous device. Even if it’s a creaky old pre-Pro iPad, it’s likely that it will outperform Apple’s powerhouse flagship device for making music. Which is utterly ridiculous (and utterly impossible if you sold the old one to upgrade to the new iPad Pro).

We have contacted Apple for comment.