Using AVAudioPlayer and AVAudioEngine on multiple threads

I'd like to move some operations involving AVAudioPlayer - and possibly AVAudioEngine, although that's less important - off the main thread using a serial dispatch queue or similar mechanism. Here's a simple self-contained example of what I'm talking about:

import AVFoundation
import UIKit

class ViewController: UIViewController {
    let player = try! AVAudioPlayer(
        contentsOf: Bundle.main.resourceURL!.appendingPathComponent("audio.m4a")
    )
    let queue = DispatchQueue(label: "", qos: .userInteractive)

    override func touchesBegan(_ touches: Set, with event: UIEvent?) {
        queue.async {
            if self.player.isPlaying {
                self.player.stop()
                self.player.currentTime = 0.0
            } else {
                self.player.play()
            }
        }
    }
}

In this example, an AVAudioPlayer instance is created on the main thread, and then subsequent operations are performed on other threads using a serial queue.

Is it safe to use AVAudioPlayer, or related tools like AVAudioEngine, in this way? Again, all operations on these objects would be serial, never concurrent.