Audio Musical Note

You know the frequency of A4 is 440 Hz. Do you know the frequency of F#3 without looking it up? Probably not, and you shouldn't have to - that's exactly the math this node does for you. Audio Musical Note (SET_AudioMusicalNote) converts a note name plus an octave into the frequency in Hz, and it's designed to feed straight into the Audio Test Signal Generator so you can generate actual musical notes instead of random tones.

Inputs

Two inputs, both forgiving:

• note - the note name, in American notation. It's case-insensitive and flexible, which is nicer than it has any right to be. "C#", "Db", "g sharp", "a flat" all parse fine - the README explicitly lists spellings like "C#", "Db", "g sharp" and "a flat" as valid. Type the sharp or the flat, spelled out or abbreviated, uppercase or lowercase; it'll figure it out.
• octave - an integer from 0 to 8. Octave 4 is the standard middle range, the one that contains A4 = 440 Hz. Middle C is C4.

Output

frequency - a FLOAT in Hz. That's it. One number, ready to plug into the Test Signal Generator's frequency input.

Why you'd reach for it

The practical reason is the chord trick. The pack's generate_and_blend.json example builds a chord by wiring four Musical Note nodes (say C4, E4, G4) into four Test Signal Generators, then blending the results with Audio Blend. With this node, building an A minor chord means typing A, C, E - not recalling 220, 261.63, 329.63. It also turns music into something programmable: an integer octave input can be driven by a counter or a slider, letting you sweep a note up and down the octaves without retyping anything.

Beyond music, it's just a sanity check tool. Need a specific calibration tone? Type the note, get the Hz, done. It's a 10-second node that saves you from either remembering equal-temperament math or googling a frequency table mid-workflow.

Install & gotchas

It ships with the Audio Batch pack. ComfyUI Manager search "Audio Batch", or:

cd ComfyUI/custom_nodes/
git clone https://github.com/set-soft/ComfyUI-AudioBatch
pip install seconohe

Restart ComfyUI. No models, no dependencies beyond what the pack already uses.

Honest limitations: it works in equal temperament with A4 = 440 Hz (standard concert pitch - if you're playing against a 432 Hz-tuned instrument, this node won't match it), and it outputs a frequency, not an actual sound - you still need the generator to hear anything. Also, there's no frequency-to-note inverse here; if you have a Hz value and want the note name, you're on your own for now. Small node, small scope, does the one thing cleanly.