Here's what appeared on porn site xhamster.com once newer versions of Chromium got around to implementing the permission check (SFW-ish):
Especially in the porn industry where the end users are likely using incognito mode or a VPN.
A lot of people also do have a virtual MIDI device installed whether they know about it or not. The name of this device differs between different operating systems and operating system revisions.
Edit: I see the disconnect now. I'm not saying Google/chrome added the midi API for fingerprinting. I'm saying the screenshot way up this thread is an example of a site using it for that purpose.
I get different types of failures and messages from different versions of Chrome, Firefox, and IE. None of which have any midi devices. Those errors, or the structure of the resulting object if it succeeds, are all fingerprint inputs.