https://www.youtube.com/watch?v=cy9kgSdjdZk

leafac_iddqdsound_flo_Pitch Tracking copy.jsfx

slider1:frequency=0<20,20000,1>Frequency

@init

zero_crossing_state = 0;
period.samples = 0;
sample.previous = 0;

@sample

sample = spl0;

period.samples += 1;

sign(sample) != sign(sample.previous) ? (
  zero_crossing_state += 1;
  
  zero_crossing_state == 2 ? (
    period.samples -= 1;
    period.samples += (abs(sample) - abs(sample.previous) + 1) / 2;
    frequency = srate / period.samples;
    zero_crossing_state = 0;
    period.samples -= floor(period.samples);
  );
);

sample.previous = sample;

leafac_iddqdsound_flo_Pitch Tracking.jsfx

slider1:threshold.db=-40<-80,+6,0.1>Threshold (dB)

slider3:frequency=0<20,20000,1>Frequency (Hz)
slider4:midi_note=0<0,127,1>MIDI Note

@init

window.length.ms = 100;
window.length.samples = window.length.ms * srate / 1000;
// window.length.samples = 2048;
zero_crossings.count = 0;
zero_crossings.circular_buffer = 0;
zero_crossings.circular_buffer.index = 0;
sample.previous = 0;
zero_crossings.allowed = 0;

@slider

threshold.linear = 10^(threshold.db / 20);

@sample

sample = spl0;

zero_crossings.count -= zero_crossings.circular_buffer[zero_crossings.circular_buffer.index];

abs(sample) > threshold.linear ? zero_crossings.allowed = 1;

zero_crossings.allowed && sign(sample) != sign(sample.previous) ? (
  zero_crossings.allowed = 0;
  zero_crossings.circular_buffer[zero_crossings.circular_buffer.index] = 1;
  zero_crossings.count += 1;
) : (
  zero_crossings.circular_buffer[zero_crossings.circular_buffer.index] = 0;
);

frequency = (zero_crossings.count / 2) / window.length.ms * 1000;
midi_note = 12 * log(frequency/440) / log(2) + 69;

zero_crossings.circular_buffer.index += 1;
zero_crossings.circular_buffer.index == window.length.samples ? zero_crossings.circular_buffer.index = 0;

sample.previous = sample;