I'm using the following semitone lever systems on my harps:

• Soundiamonds™ I
  This reliable system was developed by myself; it was optimised for purity of sound, based on the fork disc mechanism that is also used on pedal harps.
  
  
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  360° View (QuickTime)

  
  
• Soundiamonds™ II
  Like type I, but based on a slightly simpler principle.
  
  
  
  
  
  
  
  
  

  Type "Peter Brough"

• Bronce Semitone Levers
  Quick and elegant system by Peter Brough.