title: CoreMIDI track accessing time signature information
body: <p>I'm designing a rhythm game which is driven by a MIDI track. The MIDI messages trigger the release of on-screen elements. I am loading the MIDI data from a file and then playing it using a MusicSequence and MusicPlayer. </p>
  
  <p>I understand that MIDI files contain time and key signature information as meta messages at the start of the file. However I've not found a way to retrieve this information from either the MusicPlayer or the MusicSequence. </p>
  
  <p>The information I need is the number of seconds it take to play a quaver, crotchet etc... I would expect this to be affected by the time signature and the MusicPlayerPlayRateScalar value. </p>
  
  <p>It look like this information can be found in the <a href="http://developer.apple.com/library/mac/#documentation/MusicAudio/Conceptual/CoreAudioOverview/WhatsinCoreAudio/WhatsinCoreAudio.html" rel="nofollow">CoreAudio clock</a> but I've not been able to work how this is accessed for a particular music sequence. </p>
  
  <p>Are there any CoreAudio experts out there who know how to do this?</p>