Mattermost - Mattermost is an open source alternative to Slack.
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Guitar Pro 7 - Create, play and share your tabs
Slack - A messaging app for teams who see through the Earth!
LilyPond - GNU LilyPond is a computer program for music engraving.