The Media Overlay Component will provide a button at the corner of every iframe.
This way you can pop out any iframe into a separate little window, and keep it on top while browsing through the forum, until the user closes it.
Enable that Theme Component, and whitelist your iframe source (i.e. https://w.soundcloud.com and https://api.soundcloud.com) in your site settings under allowed iframes.
Then you can paste this snippet into a Topic Post…
<iframe src="https://w.soundcloud.com/player/?url=https://api.soundcloud.com/tracks/129053679&color=ff5500&auto_play=false&hide_related=false&show_comments=false&show_user=true&show_reposts=false" height=100%></iframe>
Click that button and that mini player pops up in the bottom right corner and stays open while you browse around the site (until you manually close it)…
