Bandlab - Capture, nurture, and collaborate on song ideas in the cloud
AIVA - The AI composing emotional soundtrack music
Soundscape - Sync your music with the open source community
WolframTones - Listen to what I just found in the WolframTones music universe
Krue - Twitch for music: live streams from amazing musicians
WaveBots Editor - Procedural music and sound maker that exports to Wav, MIDI, GoatTracker and much more.