I was looking for the reason that AudioComponentInstanceNew() returned -10863(kAudioUnitErr_CannotDoInCurrentContext) for an AudioUnit, which was created using target template on Xcode 7.3.
The AudioUnit was also failed a validation with auvaltool -v.
$ auvaltool -v aufx vibr Symi
AU Validation Tool
Version: 1.6.1a1
Copyright 2003-2013, Apple Inc. All Rights Reserved.
Specify -h (-help) for command options
--------------------------------------------------
VALIDATING AUDIO UNIT: 'aufx' - 'vibr' - 'Symi'
--------------------------------------------------
Manufacturer String: Shakeyama
AudioUnit Name: VibratoUnit
Component Version: 1.6.0 (0x10600)
* * PASS
--------------------------------------------------
TESTING OPEN TIMES:
COLD:
Time to open AudioUnit: 333.540 ms
WARM:
Time to open AudioUnit: 101.261 ms
This AudioUnit is a version 3 implementation.
FIRST TIME:
FATAL ERROR: Initialize: result: -50
From the message above, it was found that the AudioUnit seemed version 3.
For version 3 AudioUnit, for example, it can be initialized using AVAudioUnit.instantiateWithComponentDescription() in Swift.
Reference: Shared/SimplePlayEngine.swift
After further survey, I confirmed that the AU can be initialized using +[AUAudioUnit instantiateWithComponentDescription:options:completionHandler:] in Obj-C, or AudioComponentInstantiate() in C, as well.
Note that these initialization was done asynchronously.
So, you will need modify your host code to write post-initalization code in Blocks.
By the way, if you want to make version 2 AudioUnit, Audio Unit Examples (AudioUnit Effect, Generator, Instrument, MIDI Processor and Offline) may help.
I think this way will be easer...
