Note2Freq

A lightweight utility audio plugin that displays note frequencies and their harmonic relationships. Perfect for tuning drums, EQ work, and understanding the frequency spectrum of musical notes.

Features

• Note Selection: Choose any note (C, D, E, F, G, A, B) with sharp or flat modifiers
• Frequency Display: Shows frequencies for all octaves (0-10) based on A440 standard tuning
• Harmonic Relationships: Display 3rd (major/minor) or 5th intervals to find harmonically pleasing frequencies
• Zero Latency: Audio passes through untouched with no processing or latency
• Minimal CPU Usage: Extremely lightweight, perfect for keeping open during mixing/production

Use Cases

• Drum Tuning: Find harmonically pleasing frequencies to tune toms and other drums
• EQ Reference: Quickly identify which frequencies correspond to specific notes
• Sound Design: Understand the harmonic relationships between notes
• Mixing: Make informed decisions about frequency boosts/cuts based on the song's key

Installation

Grab the latest build for your platform from Releases — each one ships both a raw zip and a native installer:

• macOS: Note2Freq-macOS-vX.Y.Z-Installer.pkg (signed & notarized, installs AU + VST3) or the .zip if you'd rather place the bundles yourself
• Windows: Note2Freq-Windows-vX.Y.Z-Installer.exe (VST3) or the .zip
• Linux: Note2Freq-Linux-vX.Y.Z-Installer.deb (VST3) or the .zip

Then rescan plugins in your DAW.

Usage

1. Select Root Note: Click on the desired note (C-B)
2. Add Accidentals (optional): Click sharp (#) or flat (b) to modify the note
3. Choose Harmony (optional): Select 3rd or 5th to display harmonic intervals
4. Select Quality (optional): For 3rds, choose Major or Minor (5ths are always perfect)

The plugin displays frequencies for all octaves (0-10) in an easy-to-read grid format, with bold octave numbers above each frequency value.

Building from Source

Requirements

• CMake 3.22+
• macOS (Xcode) for AU + VST3, or Windows/Linux for VST3 only

Build Instructions (CMake)

1. Clone the repository with submodules: git clone --recurse-submodules <repo-url>
2. cmake -B build -DCMAKE_BUILD_TYPE=Release (omit -DCMAKE_BUILD_TYPE on Windows)
3. cmake --build build --config Release --parallel
4. Artefacts land at build/Note2Freq_artefacts/Release/AU/Note2Freq.component (macOS only) and build/Note2Freq_artefacts/Release/VST3/Note2Freq.vst3

CI builds macOS/Windows/Linux and validates the AU with auval on every push; releases are built, signed (macOS), notarized, packaged into installers, and published from GitHub Actions (see .claude/rules/build.md).

Build Instructions (Projucer, for local editing)

1. Open Note2Freq.jucer in Projucer
2. Generate Xcode project
3. Build in Xcode (use Release configuration for optimised build)

Technical Details

• Format: AU (Audio Unit, macOS) and VST3 (macOS, Windows, Linux)
• Type: Audio Effect Plugin
• Processing: Zero-latency passthrough
• Tuning Reference: A440 (440 Hz)
• Octave Range: C0 (16.35 Hz) to C10 (16,744.04 Hz)

Optimisation

The Release build includes aggressive optimisations:

• Dead code stripping
• Link-time optimisation
• Symbol stripping
• Minimal binary size

Licence

Created by Leigh Pierce

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Note: This is a reference/utility plugin and performs no audio processing. It's designed to stay open in your session as a quick reference tool.