Ha! There is a Working Draft for interfacing with MIDI devices in the browser. That is so cool. Unfortunately, only Chrome (and Chromium) has support for it yet.
Web MIDI API gives you low-level access to the midi messages stream for any MIDI controller connected to your computer. Today, most E-Piano or Keyboards come with an USB port.
Try it out here: https://eliogubser.com/chord/
Here’s a video of it in action:
Source Code: https://github.com/gubser/chord/blob/master/chord.js