Recognize played chords in audio

Learn how to create requests for chord recognition in audio files.

1. Selecting vocabulary

You can restrict the vocabulary used for the chord recognition. Currently there are the following two options to choose from:

Vocabulary	Regex for possible values
major-minor	^((N|X){1}$)|\((C|C#|D|D#|E|E#|F|F#|G|G#|A|A#|B|B#){1}(:(min|maj))?\)$
full	^((N|X){1}$)|\((C|C#|D|D#|E|E#|F|F#|G|G#|A|A#|B|B#){1}(:(min|maj|dim|aug|min6|maj6|min7|maj7|minmaj7|7|dim7|hdim7|sus2|sus4))?\)$

N: no chord X: Unknown Chord

Using the reduced major-minor vocabulary yields a better hit-rate compared to the full vocabulary. Choose the vocabulary based on your needs.

2. Request via API

  import requests
  
  API_KEY = 'YOUR_KLANGIO_API_KEY'


  audio_file = open('{YOUR_FILE_NAME}', 'rb')

  query_parameters = {
    'vocabulary': 'major-minor', # required
    'webhook_url': '{YOUR_WEBHOOK_ENDPOINT_URL}' # optional, but recommended
  }

  multipart_params = {
    'file': audio_file
  }

  resp = requests.post(
    'https://api.klang.io/chord-recognition',
    headers={
        'kl-api-key': API_KEY
    },
    params=query_parameters,
    files=multipart_params
  )

  if resp.status_code = 200:
    print(resp.json())
    # {
    #  'job_id': 'SOME_JOB_ID', 
    #  'creation_date': '2023-01-01', 
    #  'deletion_date': '2023-02-01',
    #  'status_endpoint_url': 'https://api.klang.io/job/{SOME_JOB_ID}/status'
    # }

3. Result format

The chord recognition detects the chords within time intervals of the audio file and returns you the list of start- and end-times of such an interval with the detected chord.

The job result is a json array, containing only triplet entries [<start_time_in_seconds>, <end_time_in_seconds>, <chord_name>] with the type [float, float, string]. The chord_name contains the values in range of the specified vocabulary.

Example:

[
    [
        0.0,
        1.0185185185185184,
        "N"
    ],
    [
        1.0185185185185184,
        3.2407407407407405,
        "E:maj"
    ],
    [
        3.2407407407407405,
        3.518518518518518,
        "D#:maj"
    ],
    [
        3.518518518518518,
        5.7407407407407405,
        "E:maj"
    ],
    [
        5.7407407407407405,
        6.018518518518518,
        "D#:maj"
    ],
    [
        6.018518518518518,
        7.222222222222221,
        "N"
    ],
    [
        7.222222222222221,
        9.537037037037036,
        "E:maj"
    ],
    [
        9.537037037037036,
        10.0,
        "D#:maj"
    ],
    [
        10.0,
        12.314814814814815,
        "E:maj"
    ],
    [
        12.314814814814815,
        15.0,
        "N"
    ]
]