This repository contains a python package to compute distribution-based quality metrics for audio data using embeddings, with a focus on music.

It features the following metrics:

• Accompaniment Prompt Adherence (APA, see https://arxiv.org/abs/2503.06346 )

• Fréchet Distance (see https://arxiv.org/abs/1812.08466 )

• Kernel Distance/Maximum Mean Discrepancy (see https://arxiv.org/abs/1812.08466 )

• Density and Coverage (see https://arxiv.org/abs/2002.09797 )

The measures have in common that they compare a set of candidate audio tracks against a set of reference tracks, rather than evaluating individual tracks, and they all work on embedding representations of audio, obtained from models pretrained on tasks like audio classification.

The first two measures are typically used to measure audio quality (i.e. the naturalness of the sound, and the absence of acoustic artifacts). Density and Coverage explicitly measure how well the candidate set coincides with the reference set by comparing the embedding manifolds.

The Accompaniment Prompt Adherence measures operates on sets whose elements are pairs of audio tracks, typically a mix and an accompaniment, and quantifies how well the accompaniment fits to the mix.

The measures can be combined with embeddings from any of the following models:

• VGGish - https://arxiv.org/abs/1609.09430 Trained on audio event classification. 128-dimensional embeddings from the last feature layer before the classification layer.

• Laion CLAP - https://github.com/LAION-AI/CLAP using either the checkpoint trained on music and speech, or the checkpoint trained on music only; Embeddings from the last three layers (512, 512, and 128-dimensional)

Install from PyPI:

pip install audio-metrics

To run the examples, install with the examples dependencies:

pip install 'audio-metrics[examples]'

For development or to use the latest version from source:

git clone https://github.com/SonyCSLParis/audio-metrics.git
cd audio-metrics
pip install -e '.[dev]'

The following examples demonstrate the use of the package. For more examples see ./examples directory.

import numpy as np
from audio_metrics import AudioMetrics

sr = 48000
n_seconds = 5

n_windows = 100
window_len = sr * n_seconds

# create random audio signals
reference = np.random.random((n_windows, window_len))
candidate = np.random.random((n_windows, window_len))

metrics = AudioMetrics(
    metrics=[
        "prdc",  # precision, recall, density, coverage
        "fad",  # frechet audio distance
        "kd",  # kernel distance
    ],
    input_sr=sr,
)
metrics.add_reference(reference)

print(metrics.evaluate(candidate))

# To compute APA, the input data must be pairs of context and stem (in the
# trailing dimension)
reference = np.random.random((n_windows, window_len, 2))
# Data can also be passed as a generator, to facilitate processing larger
# datasets
candidate = (np.random.random((window_len, 2)) for _ in range(n_windows))

# stem-only metrics (like FAD), can be computed simultaneously with APA
metrics = AudioMetrics(
    metrics=["fad", "apa"],
    input_sr=sr,
)
metrics.add_reference(reference)
print(metrics.evaluate(candidate))

When computing APA the reference and candidate sets must be pairs of context and stem. Note that when FAD and/or PRDC are computed as additional metrics, these are only computed for the stems (the contexts are ignored for these metrics).

To cite this work, please use:

M. Grachten and J. Nistal. (2025). Accompaniment Prompt Adherence: A Measure for Evaluating Music Accompaniment Systems. Proceedings of the International Conference on Acoustics, Speech, and Signal Processing. IEEE. Hyderabad, India.

@inproceedings{grachten2025accompaniment,
  title        = {Accompaniment Prompt Adherence: A Measure for Evaluating Music Accompaniment Systems},
  author       = {Grachten, Maarten and Nistal, Javier},
  booktitle    = {ICASSP 2025-2025 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)},
  pages        = {1--5},
  year         = {2025},
  organization = {IEEE},
  address      = {Hyderabad, India}
  month        = apr
}