Convert a note + octave to its frequency.

note_to_freq.py

# MIT License
# Python to convert a string note (eg. "A4") to a frequency (eg. 440).
# Inspired by https://gist.github.com/stuartmemo/3766449

def getFrequency(note, A4=440):
    notes = ['A', 'A#', 'B', 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#']

    octave = int(note[2]) if len(note) == 3 else int(note[1])
        
    keyNumber = notes.index(note[0:-1]);
    
    if (keyNumber < 3) :
        keyNumber = keyNumber + 12 + ((octave - 1) * 12) + 1; 
    else:
        keyNumber = keyNumber + ((octave - 1) * 12) + 1; 

    return A4 * 2** ((keyNumber- 49) / 12)

💯

GIves me an error:

did you manage to fix that? If not, can you share notes.py here?

@lafkpages I think you need to include two characters, the note name and the octave, otherwise the program would have no idea which octave to use.

Alternatively,

NOTES = ['A', 'Bb', 'B', 'C', 'Db', 'D', 'Eb', 'E', 'F', 'Gb', 'G', 'Ab']

def pitch2freq(pitch, A4=440):
    note = NOTES.index(pitch[:-1])
    octave = int(pitch[-1])
    distance_from_A4 = note + 12 * (octave - (4 if note < 3 else 5))

    return A4 * 2 ** (distance_from_A4/12)