TuneLab Pro is a professional piano tuning tool. When the proper note is sounded in the microphone of the computer, the program will show how that note compares with its ideal pitch using two different displays.
The "phase display" contains squares that move to the left or the right to indicate that the note is flat or sharp. The "spectrum display" is a graph of the distribution of audio energy across the frequency spectrum. This display can be switched between a wide view of the entire spectrum and three different levels of a narrow zoomed-in view centered around the selected note and partial.