getUserMedia() mutes audio output in Chrome for Mobile

Question

I want to develop a web App for mobile phones that records audio from the microphone and plays music at the same time.

With getUserMedia() I get the stream and create in my AudioContext a MediaStreamSource. At the same time I create a BufferSource which plays music. In Chrome this setup works. But when I start the same Web app in Chrome on my Nexus 5 and I allow it to use the microphone the music is muted.

Success Callback for getUserMedia:

function gotStream(stream) {
  mediaStreamSource = audioContext.createMediaStreamSource(stream);
  meter = createAudioMeter(audioContext);
  mediaStreamSource.connect(meter);
  info = document.getElementById('info');
  outputData(); 
}

Play Music Function:

function playSound(buffer) {
  source = audioContext.createBufferSource();
  source.buffer = buffer;
  gainNode = audioContext.createGain();
  source.connect(gainNode);
  gainNode.connect(audioContext.destination);
  source.start(0);
}

Should that be the expected behaviour or am I doing something wrong?