Open Radar

 
Summary:
iOS apps that provide MIDI functionality but don't have their own audio engines cannot be used in the background. This would be addressed by the addition of a new MIDI background mode.

Notes:
Music production on iOS is becoming steadily more popular and sophisticated. Use of background audio is becoming more common, particularly with the advent of the Audiobus inter-app audio technology.

However, there is currently no "background MIDI" functionality on iOS. This means apps that don't have their own audio engines, but generate or manipulate MIDI for other apps are severely limited in a multi-app iOS music production environment.

Consequently, if such apps wish to be usable in such an environment, they are forced to add an audio engine to make use of the audio background mode, which is wasteful and counter to the goals of iOS' multitasking environment.

Examples of such apps include:

 - Genome MIDI sequencer, a pattern based MIDI sequencer that generates MIDI for other apps (http://itunes.apple.com/us/app/genome-midi-sequencer/id450475494?mt=8)

  Genome has an audio engine, but does not currently generate any audio at all - its audio engine emits silence, and exists only to allow the app to run in the background using the audio background mode. The next version is going to have audio generation.

 - iMIDIPatchBay, a meta-controller app that lets users split signals from a MIDI controller and send them to multiple destinations (https://itunes.apple.com/us/app/imidipatchbay/id622204114?l=de&ls=1&mt=8)

  iMIDIPatchBay currently remains active in the background using audio background mode by continuously playing a silent audio file.

 - Step Poly Arp, an arpeggiator that manipulates the MIDI stream from other MIDI controllers (http://itunes.apple.com/us/app/steppolyarp-midi-step-polyphonic/id395484905?mt=8)

  Step Poly Arp has a simple synth audio engine with limited use except as a reason to be allowed to use the audio background mode.

With these apps unable to run in the background without an audio engine, users can't make use of them in a multi-app musical workflow.

Adding audio engines for the primary purpose of enabling the app to run in the background results in an enormous amount of back-and-forth between developers and the App Review team. Rejections by the App Review team are common, usually followed by appeals which are typically successful, although frequently not until multiple cycles of rejection and appeal have been completed.

Introducing a new multitasking background mode for MIDI would enable apps like this to remain active in the background, allowing them to be a part of a multi-app workflow while not unnecessarily consuming resources by running an audio engine for the sole purpose of using the audio background mode.