Ios 为什么AudioKit中的音序器不能播放我的鼓声，为什么音量这么低？

首先，一个伟大的框架。这是一手让我从硕士课程毕业。还有，我是赞助商！任何帮助都会受到感激。我还可以推送我的存储库并在GitHub上共享，以便更仔细地查看

不管怎样，这是我的代码

import Foundation
import AudioKit

class DrumSounds {

    let drums = AKMIDISampler()
    var currentBPM = 60
    var rideCymbalFile: AKAudioFile?
    var snareDrumFile: AKAudioFile?
    var bassDrumFile: AKAudioFile?
    var hiHatFile: AKAudioFile?
    let sequencer = AKAppleSequencer(filename: "4tracks")
    var booster = AKBooster()
    init() {

        do{

        try rideCymbalFile = AKAudioFile(readFileName: "rideCymbalSound.wav")
        try snareDrumFile = AKAudioFile(readFileName: "snareDrumSound.wav")
        try bassDrumFile = AKAudioFile(readFileName: "bassDrumSound.wav")
        try hiHatFile = AKAudioFile(readFileName: "hiHatSound.mp3")
        try drums.loadAudioFiles([rideCymbalFile!,
                                   snareDrumFile!,
                                   bassDrumFile!,
                                   hiHatFile!])

        } catch {
            print("error loading samples to drum object")
        }

        drums.volume = 1
        booster = AKBooster(drums)
        AudioKit.output = drums
        sequencer.clearRange(start: AKDuration(beats: 0), duration: AKDuration(beats: 100))
        sequencer.debug()
        sequencer.setGlobalMIDIOutput(drums.midiIn)
        sequencer.enableLooping(AKDuration(beats: 4))
        sequencer.setTempo(Double(currentBPM))

    }

    func playDrumSounds () {

        do {
            try AKSettings.setSession(category: .playAndRecord, with:  AVAudioSession.CategoryOptions.defaultToSpeaker)

            let session = AVAudioSession.sharedInstance()
            try session.setCategory(AVAudioSession.Category.playAndRecord)

            if !AKSettings.headPhonesPlugged {
                try session.overrideOutputAudioPort(AVAudioSession.PortOverride.speaker)
         }
        }catch {
            print("error in settings.setSession")
        }

        sequencer.tracks[0].add(noteNumber: 0, velocity: 127, position: AKDuration(beats: 0), duration: AKDuration(beats: 1.0))
        sequencer.tracks[0].add(noteNumber: 0, velocity: 127, position: AKDuration(beats: 1), duration: AKDuration(beats: 1.0))
        sequencer.tracks[0].add(noteNumber: 0, velocity: 127, position: AKDuration(beats: 2), duration: AKDuration(beats: 1.0))
        sequencer.tracks[0].add(noteNumber: 0, velocity: 127, position: AKDuration(beats: 3), duration: AKDuration(beats: 1.0))
        sequencer.play()

    }   
}

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我在另一篇帖子中偶然发现一条评论，就明白了这一点。音量较低，因为您需要在“签名和功能”下启用背景模式下的音频、播放和画中画。单击左上角的+按钮以添加功能：

至于演奏正确的鼓声：事实上，演奏的是正确的鼓声。但是我把MIDI的音符设置得太低了，所以听起来像是刺耳的静电。如果您遇到这个问题，并且从未像我这样使用过MIDI，这里有一个指向MIDI音符编号描述的链接：。数字越大，频率越高。更改MIDI音符编号将更改音频文件的频率