SongProcessor AudioKit - hack to play multiple files at once

JPMixer.swift

//
//  Mixer.swift
//  SongProcessor
//
//  Created by Pope, John on 8/10/17.
//  Copyright © 2017 AudioKit. All rights reserved.
//

import Foundation
import AudioKit

extension AKAudioPlayer{
    func isMuted()->Bool{
        if (self.volume > 0){
            return false
        }else{
            return true
        }
    }
    
    func unmute(){
        self.volume = 1
    }
    func mute(){
        self.volume = 0
    }
}


class JPMixer{
    static let shared = JPMixer()
    
    var audioFiles: [AKAudioFile] = []
    var audioPlayers: [AKAudioPlayer] = []
    
    var mixer:AKMixer!
    var audioFilePlayer: [AKAudioPlayer]  = []

    func build()->AKMixer?{

        if let files = try? FileManager.default.contentsOfDirectory(atPath: Bundle.main.bundlePath ){
            for file in files {
                if file.hasSuffix("caf"){
                    if let audioFile = try? AKAudioFile(readFileName:file, baseDir: .resources){
                        audioFiles.append(audioFile)
                        if let audioFilePlayer = try? AKAudioPlayer(file: audioFile)
                        {
                            audioFilePlayer.looping = true
                            audioPlayers.append(audioFilePlayer)
                        }else{
                            print("FAILED to add fileplayer")
                        }
                    }else{
                        print("FAILED to find file")
                    }
                }
            }
        }
   
        mixer = AKMixer(audioPlayers)
        mixer.stop()
        return mixer
    }
    func playMix(){
        mixer.stop()
        print("isStarted:",mixer.isStarted)
        print("isPlaying:",mixer.isPlaying)
        
        for players in audioPlayers{
            players.play()
        }
        // failed attempt to have all players play at same time.
        for players in audioPlayers{
            players.startTime = 0
        }
        print("isStarted:",mixer.isStarted)
        print("isPlaying:",mixer.isPlaying)
        mixer.start()

        
    }
    func playFile(_ fileName:String){
        for players in audioPlayers{
            let fullname = "\(fileName).caf"
            if (players.audioFile.fileName == fileName){
                players.unmute()
            }else if (players.audioFile.fileName == fullname){
                players.unmute()
            }
        }
    }
}

SongProcessor.swift

//
//  SongProcessor.swift
//  SongProcessor
//
//  Created by Aurelius Prochazka on 6/22/16.
//  Copyright © 2016 AudioKit. All rights reserved.
//

import UIKit
import AudioKit
import MediaPlayer

class SongProcessor {

    static let sharedInstance = SongProcessor()

    var audioFile: AKAudioFile!
    var mixer:AKMixer!
    var audioFilePlayer: AKAudioPlayer!
    var variableDelay: AKVariableDelay!
    var delayMixer: AKDryWetMixer!
    var moogLadder: AKMoogLadder!
    var filterMixer: AKDryWetMixer!
    var reverb: AKCostelloReverb!
    var reverbMixer: AKDryWetMixer!
    var pitchShifter: AKPitchShifter!
    var pitchMixer: AKDryWetMixer!
    var bitCrusher: AKBitCrusher!
    var bitCrushMixer: AKDryWetMixer!
    var playerBooster: AKBooster!

    var currentSong: MPMediaItem?
    var isPlaying: Bool?

    init() {
        audioFile = try? AKAudioFile(readFileName: "Bass.caf", baseDir: .resources)
        audioFilePlayer = try? AKAudioPlayer(file: audioFile)
        audioFilePlayer?.looping = true


        startVariableDelay()
        startMoogLadder()
        startCostelloReverb()
        startPitchShifting()
        startBitCrushing()

        //Booster for Volume
        //playerBooster = AKBooster(bitCrushMixer, gain: 0.5)

       
        
        // Mixer
        if let jpMixer = JPMixer.shared.build(){
           mixer = jpMixer
        }

        AudioKit.output = mixer
        AudioKit.start()
        
        
    }

    func startVariableDelay() {
        variableDelay = AKVariableDelay(audioFilePlayer)
        variableDelay?.rampTime = 0.2
        delayMixer = AKDryWetMixer(audioFilePlayer, variableDelay, balance: 0)
    }

    func startMoogLadder() {
        moogLadder = AKMoogLadder(delayMixer)
        filterMixer = AKDryWetMixer(delayMixer, moogLadder, balance: 0)

    }

    func startCostelloReverb() {
        reverb = AKCostelloReverb(filterMixer)
        reverbMixer = AKDryWetMixer(filterMixer, reverb, balance: 0)
    }

    func startPitchShifting() {
        pitchShifter = AKPitchShifter(reverbMixer)
        pitchMixer = AKDryWetMixer(reverbMixer, pitchShifter, balance: 0)
    }

    func startBitCrushing() {
        bitCrusher = AKBitCrusher(pitchMixer)
        bitCrusher?.bitDepth = 16
        bitCrusher?.sampleRate = 3_333
        bitCrushMixer = AKDryWetMixer(pitchMixer, bitCrusher, balance: 0)
    }

}

Hi John, I think we're both trying to achieve similar functionality right now.

Is play(from: to: avtime:) suitable for your needs?

let scheduledTime = 0.1 //time in seconds until playback begins
let hostTime = mach_absolute_time()
let avTime = AKAudioPlayer.secondsToAVAudioTime(hostTime: hostTime, time: scheduledTime)

amlBassPlayer.play(from: 0.0, to: audioFile.duration, avTime: avTime);

try the develop branch of audiokit
https://github.com/AudioKit/AudioKit/tree/develop/Examples/iOS/SongProcessor/SongProcessor

I got distracted with work haven't had a chance to progress things.
I do know that the AmazingAudioEngine worked flawlessly in obj-c / I could load > 300mb of caf files no problem.
Tell me that this works for you. if you find a bug - log an issue - audiokit team are actively working on this.