Nice work! It might be nice to hint to iOS users that they should disable silent mode via the little side toggle if they want to hear anything. Just a quirk of iOS that took me literally years to figure out -- I assumed it just didn't support the Web Audio API and went on with my life.
Or as the developer you can play some silent audio in the background via an ` ` element: https://github.com/donbrae/onscreen-piano-keyboard/blob/main... . This will ensure the Web Audio API produces sound even with the ‘silent’ switch active.
Coincidentally someone asked me about this the other day so I put together a minimal demo here in case it's useful to anyone: https://codepen.io/matteason/pen/VYwdzVV