Create, play back and print beautiful sheet music with free and easy to use music notation software MuseScore. For Windows, Mac and Linux 

https://musescore.org/en 

Flat: Online collaborative music notation software

Create, compose, collaborate, play, and print your sheet music using the world's most simple and intuitive web-based music writing and composition software.

Noteflight is an online app that allows users to compose, view, and share music notation from any web browser. However, rather than basic composition software, Noteflight allows users to edit, print, and playback written music from any connected device.

Band Lab music creation features let you embark on a music-learning journey that unleashes your creativity. 

https://edu.bandlab.com/