CalAr is a free graphic harmonic calculator software licensed under GNU GPLv3.
System requeriments:
Java Runtime Environment 1.6 or above.
Screen of at least 1024x600px.
Optional: A Java Sound Bank.
The program allows you to select one of 108 notes from a keyboard indicating the harmonic quantity to consider (1-32). Then displays the frequency for the fundamental and each harmonic, and shows the tuning error with a graphic indicator.
About the graphic indicator's placement algorithm
OS tests