Plink
Plink focuses on playing a browser instrument with others.
What it does
Plink allows several people to play music together in a browser.
When to use it
During a remote hangout, try an improvised session without a prepared score.
Visit Plink official site
Amped Studio
Amped Studio focuses on browser-based recording and multitrack production.
Ardour
Ardour focuses on recording, composition, and mixing workflows.
Audacity
Audacity focuses on waveform editing, recording, and audio effects.