SMuFL is developed by the W3C Music Notation Community Group in GitHub.
If you would like to help, there are several ways you can contribute to SMuFL.
Improving classification of existing symbols, and suggesting missing symbols
If you are an expert in a particular field of music and can assist with establishing whether all of the relevant symbols have been included in SMuFL, please first review the current version of SMuFL, then join the W3C Music Notation Community Group and post your suggestions for changes and additions to the public-music-notation-contrib mailing list.
Mapping existing music fonts onto SMuFL
If you can contribute time to provide details of how the repertoires of existing music font families map onto SMuFL, please join the W3C Music Notation Community Group and ask on the public-music-notation-contrib mailing list for more information about how to create such a mapping.
Designing SMuFL-compliant music fonts
If you are a font designer and would like to contribute to the development of SMuFL-compliant music fonts, you may find it useful to review the current version of SMuFL, which includes detailed design guidelines both for fonts intended for use in scoring applications, and for fonts intended for use in text-based applications.