Question about Pandora

[Doberluv]

I down loaded Pandora, a free app on my new computer. It plays radio stations that you pick by the type of music you like. You probably already know all that. So, here's the question: Why is it, that when I have it playing in the background, but I have Chazhound or some other site on the front and Pandora behind, it plays two songs at the same time. Like right now, I have Stormy Weather and Mack the Knife. going at the same time. Arrrrggggg!. It sounds awful. When I click to have Pandora on the front and make Chazhound disappear, it works fine