Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.

tonestro - Practice & improve on your wind instrument while having fun

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

Violin by Trala - Violin by Trala is a music learning app that is designed specifically for Violin users.

Finale - Finale, the world standard for music notation software, lets you compose, arrange, notate, and print engraver-quality sheet music.

Yousician - Learn to play music at home, at your own pace