Converting frequency (Hz) to notes and back

[Bauxitedev]

I was just wondering, is it possible to convert a frequency in Hertz to the nearest note, and vice versa? If not, how would I go about doing this?

[XBagon]

I think this would require some general work on tunings to be implemented properly.
For now something like this should work (assuming A4 to be 440Hz):

fn note_nr(note: Note) -> u8 {
    note.pitch_class.into_u8() + 12 * note.octave
}

fn note_to_freq(note: Note) -> f32 {
    let a440 = note_nr(Note::new(PitchClass::A, 4));
    2f32.powf(((note_nr(note) as i16 - a440 as i16) as f32) / 12.0) * 440.0
}

fn from_note_nr(nr: u8) -> Note {
    println!("nr: {}", nr);
    let pitch_class = PitchClass::from_u8(nr % 12);
    let octave = nr / 12;
    Note::new(pitch_class, octave)
}

fn freq_to_note(freq: f32) -> Note {
    let a440 = note_nr(Note::new(PitchClass::A, 4));
    from_note_nr(((12.0 * (freq/440.0).log2()) as i16 + a440 as i16) as u8)
}

[the-drunk-coder]

I was just about to ask this, it'd come in handy. A music library that can do these conversions (like music21 in Python or CommonMusic2 in CommonLisp) is still missing in Rust, as far as I know.

[the-drunk-coder]

I added the feature as described above to my fork ... not sure if a PR is warranted ?