MuseScore is the world’s most popular music notation software. It is free and open source, and it runs on Windows, macOS, and Linux. MuseScore also provides mobile apps for viewing and playing sheet music on your phone or tablet, and it powers the world’s largest sheet music creator community at musescore.com.
I am one of the developers of MuseScore as well as the author of Mastering MuseScore, the definitive guide to this amazing software.
If you have any interest in music notation software, I encourage you to check out MuseScore!