A 12th-octave musical-pitch-centered spectrum viewer for iPad
See all the frequency harmonics from the real-time microphone input. Spectrum is displayed relative to an equal-tempered musical frequency scale. Frequencies bars are highlighted in green when on pitch and in tune (+- 20 cents). The 3 largest FFT peaks are interpolated for greater frequency accuracy readout, with the nearest note value and any pitch error estimated in cents. A fundamental pitch is also estimated, if possible, when different from the frequency of peak amplitude. Frequency range is approximately 2 octaves below middle-C to 3 or 5 octaves above, depending on the microphone used. The amplitude is in uncalibrated dB.