Not having read the C++ synchronisation primitives before, this async task queue is probably incorrect. But nevertheless, let's have a quick go at employing it — in a hideously thread unsafe fashion — for audio generation. What can possibly go wrong?

Concurrency/AsyncTaskQueue.cpp

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+//
+//  AsyncTaskQueue.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/10/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#include "AsyncTaskQueue.hpp"
+
+using namespace Concurrency;
+
+AsyncTaskQueue::AsyncTaskQueue() : should_destruct_(false)
+{
+	thread_.reset(new std::thread([this]() {
+		while(!should_destruct_)
+		{
+			std::function<void(void)> next_function;
+
+			queue_mutex_.lock();
+			if(!pending_tasks_.empty())
+			{
+				next_function = pending_tasks_.front();
+				pending_tasks_.pop_front();
+			}
+			queue_mutex_.unlock();
+
+			if(next_function)
+			{
+				next_function();
+			}
+			else
+			{
+				std::unique_lock<std::mutex> lock(queue_mutex_);
+				processing_condition_.wait(lock);
+				lock.unlock();
+			}
+		}
+	}));
+}
+
+AsyncTaskQueue::~AsyncTaskQueue()
+{
+	should_destruct_ = true;
+	enqueue([](){});
+}
+
+void AsyncTaskQueue::enqueue(std::function<void(void)> function)
+{
+	queue_mutex_.lock();
+	pending_tasks_.push_back(function);
+	queue_mutex_.unlock();
+
+	std::lock_guard<std::mutex> lock(queue_mutex_);
+	processing_condition_.notify_all();
+}
+
+void AsyncTaskQueue::synchronise()
+{
+	// TODO
+//	std::mutex
+}