Electronic Tuners
Tempering a Head
Using a different electronic tuner app on an iPhone (insTuner), on the same 72cm Fiedler timpano, when the head was tempered at a low C2, the insTuner registered the pitch as being that of C1.
Virtual Pitch-Missing Fundamental Spectogram
When sounding a C3 @130 Hz on a 72cm Fiedler timpano, the Spectogram below (click to enlarge) shows the relative frequencies for modes 1,1 through 6,1 as well as activity for the missing fundamental, which would be C2 65.41 Hz. This frequency (C2 65.41) is not a vibration that occurs in the head, but is visible in the spectrum because of the virtual pitch created by the near harmonic partials. This spectogram was generated with the SpectrumView Frequency Analysis iOS App on an iPad2.
Many electronic pitch measuring devices can be used to test accuracy of timpani pitch, provided you want the timpani pitch to be as close to harmonic as possible.