Help

To start recognizing chords, allow access to the microphone. Chords has the following limitations:

• works best in a quiet space
• works best with instruments that produces clear harmonics with few overtones
• is limited to the range between F♯₃ and E₆

About

Chords recognizes musical notes present in played audio. It runs on most modern desktop and mobile browsers.

Algorithm

To recognize notes, the following process is used:

1. The audio input is split into 4096 sample wide chunks.
2. Every ¹/₁₀ second, this buffer is transformed to a power spectrum in frequency space using a fast Fourier Transform. Frequencies that do not correspond to musical notes are discarded.
3. A new analysis series is started whenever the total power in the spectrum more than doubles between consecutive spectra.
4. Whenever an analysis series is started, a Bayes Filter is used consecutively to determine which of the notes in the spectrum are being played and which are overtones or noise. (See here for a Jupyter Notebook with examples.)

Example Spectrum showing a C₄ major. The chord is highlighted in red.

Credits

Chords is made by Tilman Roeder for the SWE Project Competition. Icons based on the In The Studio icon-set. View the project on GitHub.