使用AVAudioRecorder和AVAudioSessionCategoryPlayAndRecord忽略麦克风输入

I'm developing an iPad app with multiple AVAudioPlayer's and one AVAudioRecorder. The idea is to play the sound of the principal AvAudioPlayer like background music and touching different buttons play the sound of the others AVAudioPlayers to mix with the background music. The mixed music will be recorded by the AVAudioRecorder.I'm developing an iPad app with multiple AVAudi