A: Please check that the mute switch on your device is turned off.

Even if other apps are making sound, my apps, which allow you to play along with music in your iTunes collection have to respect the setting of the mute switch. On the iPhone, this is the switch on the side of the device.

In the iPad Settings app you can select between orientation lock or mute for the physical switch on the side of the device.

If you've selected orientation lock for the switch, then the mute is on the far left side of the task bar. Double click the home button and then slide the task bar all the way to the left.

This video explains about the assignment of the mute switch.

A: Force quit the app by double clicking on the Home button and then close it by swiping away the app.

When you relaunch the app, it should work just fine.

A: Go into the iPad Settings app, and disable the "Multitasking Gestures" feature.

If it is enabled, when you put 4 fingers on the screen, Apple completely takes over the system, stops the sound and starts switching between apps.

That's really not a good thing when playing a musical instrument app that requires 4 or more fingers, like the bagpipes.

Unfortunately, I can't disable the setting programmatically from within my apps, so you have to do it manually.

A: Somehow, you've turned on the Zoom feature on your iPad's Accesibility controls. Run the Settings app on your iPad, go into General/Accessibility, and turn Zoom off.

A: Yep, that happened. Apple broke something in iOS 8.3 and isn't going to fix it. I'm issuing updates to the apps as I have the opportunity to do so.

The sliders are actually there if you can find the control knob, but in most cases, the default values I ship with the app are just fine.

If you've changed the values and want to get back to the defaults, delete and reinstall the app.

A: Yep, that also happened. Apple broke reverb for the OpenAL APIs I use for sound at some point with iOS 7 and as of iOS 8.4 hasn't fixed it.

I'm issuing updates to the apps as I have the opportunity to do so to use the newer AVAudioEngine APIs that have working reverb, but require iOS 8.

The only suggestion for now, until I can update the apps is to disable the reverb. Most if not all the apps have a reverb switch.

Q: I'm running a CoreMIDI-compliant virtual synth app on my device, but I don't hear any sound when using your CoreMIDI control surfaces.

A: Please check that "Background Audio" is enabled on the virtual synth app you are running.

Also check that the virtual synth app has an active patch on the same MIDI channel(s) you are sending from the control surface app.