Organ Tuner for iOS, v2.7

Here is what the main tuning page looks like on the iPhone. The bar with the two black squares is called the Phase Display. The squares move left for flat and right for sharp, similar to a strobe tuner. You tune the pipe so that the pattern comes to a stop. This display is for fine-tuning. It is the most accurate tuning indicator available.
Below the current note display is a graph called the Spectrum Display. Derived from a high-resolution Fourier Transform, this display gives additional information about the distribution of sound energy across the frequency spectrum. If there are several pitches sounding at once, this graph will show a peak for each pitch.