Multiplayer Piano is an online, full 88-key piano you can play alone
or with others in real-time. Plug up your MIDI keyboard, MIDI in and
out are supported. You should be able to hear some seriously talented
piano players performing here! Join in or just chat and listen.
For good performance, Chrome is highly recommended. Firefox also
supports the requisite Web Audio API, but performance may not be as
good. Chrome has Web MIDI.
Of course, first you need to
Enable Javascript
or it won't do anything...!