ComfyUI Audio to Spectrogram

A ComfyUI custom node that converts an audio input into a spectrogram image.

Features

• Supports both Mel and Linear (STFT) spectrograms
• dB-scaled output (top 80 dB dynamic range)
• 7 built-in colormaps: inferno, magma, viridis, plasma, hot, cool, gray
• Configurable frequency range, FFT parameters, and output resolution
• Optional axes, colorbar, and title overlay
• Uses torchaudio when available; falls back to NumPy STFT automatically

Installation

Copy this directory into ComfyUI's custom_nodes folder:

ComfyUI/
└── custom_nodes/
    └── CustomNode_Bispectrum/
        ├── __init__.py
        ├── nodes.py
        └── pyproject.toml

Then restart ComfyUI. The node will appear under the audio category.

Dependencies

| Package | Required | Notes | |---|---|---| | torch | Yes | Comes with ComfyUI | | matplotlib | Yes | Used for rendering | | Pillow | Yes | Image conversion | | numpy | Yes | Array operations | | torchaudio | Recommended | Faster STFT / Mel transforms |

Install recommended dependencies:

pip install torchaudio matplotlib Pillow

Node: Audio to Spectrogram

Category: audio

Inputs

| Parameter | Type | Default | Description | |---|---|---|---| | audio | AUDIO | — | ComfyUI audio input | | use_mel | BOOLEAN | True | True = Mel spectrogram, False = Linear spectrogram | | n_fft | INT | 2048 | FFT window size (256–8192) | | hop_length | INT | 512 | Frame hop size in samples (64–2048) | | win_length | INT | 2048 | Analysis window length (256–8192) | | n_mels | INT | 128 | Number of Mel filter banks (Mel mode only) | | fmin | FLOAT | 0.0 | Minimum frequency in Hz | | fmax | FLOAT | 8000.0 | Maximum frequency in Hz (set to 0 for Nyquist) | | colormap | COMBO | inferno | Matplotlib colormap | | width | INT | 1024 | Output image width in pixels | | height | INT | 512 | Output image height in pixels | | show_axes | BOOLEAN | True | Show time/frequency axes, colorbar, and title |

Output

| Name | Type | Shape | Description | |---|---|---|---| | spectrogram | IMAGE | [1, H, W, 3] | Float32 RGB image, values in [0, 1] |

Example Workflow

1. Add a Load Audio node and load any audio file.
2. Connect its output to the audio input of Audio to Spectrogram.
3. Connect spectrogram to a Preview Image or Save Image node.
4. Adjust use_mel, fmax, and colormap to taste.

License

MIT