Function detect_pitch_frequencies 

pub fn detect_pitch_frequencies(
    frequencies: &[FloatType],
    scale: Option<&Scale>,
) -> Result<Vec<FloatType>>

Each frequency’s nearest pitch of scale (C major on C4 where none is given), and the frequency of that pitch in the octave it sounds: music21’s detectPitchFrequencies.

Errors

As normalize_input_frequency.