My chromatic tuner started misbehaving after a battery leak, and rather than agree with its assessment that every sound was B4, I decided to replace it with a software tuner. I found a wonderful fast-fourier spectrum analyzer and set about modifying it to suit my purposes. I used the technique of combining harmonics to identify the fundamental frequency as described in a paper by Mary Lourde R. and Anjali Kuppayil Saji. I also added a noise-sampling feature, some low-frequency attenuation, and a nice display.