Free Music Instrument Tuner is a free Linux program for tuning your music instrument.
It uses Qt as gui library and ALSA or JACK as sound input library.

6 views are availables:

• a small view of the captured sound
  
• an history of the pitch error
  
• an history of the sound volume
  
• the shape of the wave-length
  
• the formants
  
• a microtonal tuning view