title: Using cat to join mp3 files. What is this black sorcery?
body: <p>A friend of mine just used plain-old <code>cat</code> to concatenate two mp3 files,...</p>
  
  <pre><code>cat file1.mp3 file2.mp3 &gt; out.mp3
  </code></pre>
  
  <p>...and the resulting file is perfectly reproducible, playing one song and then the next.</p>
  
  <p>What is this black magic? What happened to headers, metadata? How can this work? The duration is even displayed correctly.</p>