Google is getting serious about generating revenue from online videos, and could significantly change the YouTube experience in the process. According to multiple sources, and as previously suggested by tech analysts, YouTube is readying two separate subscription services to launch before the end of the year. The services will include “Music Key, which has been in beta since last November, and another unnamed service targeting YouTube’s premium content creators, which will come with a paywall,” reports The Verge. “Taken together, YouTube will be a mix of free, ad-supported content and premium videos that sit behind a paywall.”