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