title: Cocoa Volume Bar
body: <p>We've probably all seen this guy before - something like a long aqua button, but with lines of different colours inside. They grow larger and change colours depending on some sort of volume. They are apparently called Audio Bars, as I found out by sniffing around the system art using ThemePark. In case you're still confused, I mean something like this (in iChat):</p>
  
  <p><img src="https://i.stack.imgur.com/jvPJs.png" alt="Audio bar"></p>
  
  <p>Is there any ready-made control that will give me this, either in the system itself, a library, or otherwise? I'm guessing I'd have to implement it myself, but I'm not entirely sure how. These images are all small capsules that can be stretched, using pieces I suppose, but I don't want to fill my app up with 3 pieces for each one of the different bar states.</p>