Multi Music Tuner：カスタマイズチューナー

This app is a tuner app that can adapt to various environments (surrounding noise, overtones of instruments, range of instruments, etc.) by selecting the algorithm for pitch detection.

●Selectable algorithms
[Fast Fourier transform] The detection time and resolution (frequency unit) are determined by the sample rate and number of samples. It is relatively resistant to environmental noise.

[Autocorrelation method] It is more resistant to noise than fast Fourier transform and has a low CPU load. However, in order to calculate the frequency, the pitch must be kept constant.

[Cepstrum method] Cepstrum analysis is suitable for capturing the tone and resonance of instruments and analyzing frequency components. However, it requires a large amount of calculations and puts a strain on processing. Also, results of octaves are often displayed.

[Perceptron method (YIN)] It can estimate the fundamental frequency with high accuracy and is resistant to noise. The disadvantages are that the accuracy of low frequency components may decrease, and accurate pitch detection may be difficult for tones that contain complex overtones. Setting the threshold is key.

[Zero-crossing method] This is a simple method that calculates the frequency from the time distance at which the waveform crosses zero. It allows for the most real-time measurement. However, it can be difficult to obtain an accurate frequency when there are instruments with many harmonics or a lot of noise. When using instruments with many harmonics, the inaccuracy can be reduced by setting the low-pass filter appropriately.