For ref, when running IRkernel Jupyter R notebooks, media objects can be embedded by making use of the shiny::tags function, that can return HTML elements with appropriate MIME types, and are renderable using _repr_html machinery (h/t @flying-sheep):

For example:

PS By the by, I notice the existence of another R kernel for Jupyter notebooks, JuniperKernel. An advantage of this over IRkernel is that it supports xwidgets, a C++ widget implementation for Jupyter notebooks akin to ipywidgets. (As far as I know, there isn’t a widget implementation for IRkernel, although maybe something can be finessed using shiny::tags and other bits of shiny machinery? ) Although I could install JuniperKernel on my Mac, I had some issues getting it to work that I haven’t had a chance to explore yet, so I don’t yet have a widgets demo…

PS having to save an audio file to then load back into the player may be a faff; that said, it looks like there may be a route to using a data URI? Not tried this yet; if you have a short reproducible demo that works, please share via the comments:-)