Does the iTube take up data every time you watch/listen to a video?

I've heard about this iTube app for iPhone and was wondering when you download/catch a song, every time you replay this song/video does it take up internet data? I'm only limited on my internet data and was wondering whether or not I would go over my plan if I were to keep listening to music through this when I'm not connected to Wi-Fi.

Anything done requiring internet not using Wi-Fi will use data.

I also would like to know if itube uses data. I'm on airplane mode listening to songs no problem. So I think that means it doesn't need data to replay.