YouTube users are doing all sorts of creative things with annotations, a feature that lets them easily add interactivity to their videos.
For best results, hit play followed by pause to let the whole video buffer locally. You can then use your keyboard keys or the channel buttons on the radio video itself to change frequencies.
It’s a clever implementation – all the music is part of the same video clip and, upon clicking the station buttons, you are merely jumping to a different location in the video.
Thanks Guy Dayan for the tip.