AVPlayerNodeSplit.swift

import UIKit
import AVFoundation

let engine = AVAudioEngine()
let player = AVAudioPlayerNode()
let mixer1 = AVAudioMixerNode()
let mixer2 = AVAudioMixerNode()
engine.attach(player)
engine.attach(mixer1)
engine.attach(mixer2)
engine.connect(player, to: [
    AVAudioConnectionPoint(node: mixer1, bus: 0),
    AVAudioConnectionPoint(node: mixer2, bus: 0)
    ], fromBus: 0, format: player.outputFormat(forBus: 0))
engine.connect(mixer1, to: engine.mainMixerNode, format: mixer1.outputFormat(forBus: 0))
engine.connect(mixer2, to: engine.mainMixerNode, format: mixer2.outputFormat(forBus: 0))

try! engine.start()
player.play()
let format = player.outputFormat(forBus: 0)
let sampleRate = format.sampleRate
var buf = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: AVAudioFrameCount(sampleRate))!
buf.frameLength = AVAudioFrameCount(sampleRate)

for ch in 0..<format.channelCount {
    let samples = buf.floatChannelData![Int(ch)]
    for n in 0..<buf.frameLength {
        samples[Int(n)] = sinf(Float(2.0 * Double.pi) * 440.0 * Float(n) / Float(sampleRate))
    }
}

player.scheduleBuffer(buf) {
    print("complete")
}