title: libsndfile usage joining and mixing .wav files
body: <p>I need help getting started with libsndfile.</p>
  
  <p>I have four .wav files (all the same sample rate).</p>
  
  <p>I want to join the first two together,then the next two together,</p>
  
  <p>Then mix the resulting 2 .wav files into one.</p>