Function read_note 

pub fn read_note(
    mono: &[f64],
    rate: SampleRate,
    note: &Note,
    others: &[&Note],
    pump: Option<&Pump>,
) -> Result<Result<NoteEnvelope, NoteSkip>, FilterError>

Reads the envelope of note from the mono mix. others are the notes that sound during it; pump is stripped first when it locks to the beat.

Errors

Returns a FilterError when a harmonic band reaches the Nyquist frequency.