First, the autoplay restriction for AudioContext landed in Chrome 66, so it's not just restricted to an iframe anymore.

Second, I navigated to the noteflight link.  I opened the dev console and the warning is shown as expected.  The rest of the steps work as you say.

Also, even though there's a warning, you can press the play button and it does play.

But, if you initiate the AudioContext with user interaction, that shouldn't happen, right?

Anyway, what I was trying to say is that when you load the page for the first time, it works fine. When you go somewhere else and then hit back, audio doesn't work, although it works in the link I sent you.

I'll send you an email with a link to a place where it doesn't, with a user and password that unfortunately I cannot make public here. 

Thanks for looking into this!

Best,
Jordi

The console message happens because you created an AudioContext but not from a user gesture.  If you had, there would be no message.  But that's a very uncommon way of using WebAudio (because it wasn't required before).  Thus, you'll always get the warning.

(We should fix this warning, but aren't really sure the best way.  It's not really bad just creating an AudioContext.  And we certainly want to minimize spamming the console with warnings about this for something that is very, very common and a valid use case.)

I don't know why you don't get the message the first time but do when going back.  I get the message on the first visit.

Ok.  jordi@noteflight.com provided me a test account to work with.  Using chromium ToT and setting the autoplay policy flag to require user activation, the console warning is displayed and clicking the play button produces no audio.

This is expected with the autoplay policy, unless noteflight updated their code to call context.resume() when pressing the play button.  (Didn't check that).

This is basically a duplicate of issue 840866.

Not sure about the issue with the "page back" button.  I'm not able to reproduce that.

Able to reproduce the issue on reported chrome version 68.0.3426.0 using Mac 10.13.1, Ubuntu 14.04 and Windows 10. Observed similar behaviour as mentioned in comment#1. As the root cause for the issue has been identified (i.e., autoplay restriction for AudioContext), hence marking it as Untriaged. From comment#4 CC'ing the owner of issue 840866 for further inputs on it. 
Removing label Needs-Bisect, Please feel free to add the label back if required.

Thanks!

Assign to johnpallet@ for further triage

This is working as intended as the autoplay policy is blocking playback.