title: How to set ticks_per_beat under MIDO to a new MIDI file?
body: <p>Reading <code>ticks_per_beat</code> under MIDO can be done via <code>mid.ticks_per_beat</code>. However, if I want to save the value of <code>ticks_per_beat</code> (e.g., 120 or 480) to a new MIDI file, how it can be done? (p.s. I can set "time signature" or "tempo" as follows. But, it seems to me that there is no relationship between these values and <code>ticks_per_beat</code>.)</p>
  
  <pre><code>track.append(MetaMessage('time_signature', numerator=4, denominator=4, clocks_per_click=24, notated_32nd_notes_per_beat=8, time=0))
  
  track.append(MetaMessage('set_tempo', tempo=100000, time=0))
  </code></pre>