How to play sound in one browser from two different sites?

Question

Opera

There are two different sites. One site - radio on the Internet, the second - talks of pilots from different cities in real time.
I wanted to make the radio channel play against the backdrop of negotiations. But it does not work in One browser - either one site reproduces, or the second, together in no way.
Plays in different browsers. But I would like to make friends and reproduce in one. I prefer Opera browser.
If anyone knows a secret way to enable sound from different sites at the same time, I will be grateful for the help.