Google 
The new service was first spotted when Google began purchasing domain names related to the phrase "music key." "youtubemusickey.com," "musickey.co.uk" and "musickey.jp" are now owned by Google. But in a series of leaked screenshots, Android Police claims to have detailed the features of the new service.
Key features of this new "premium" version of YouTube are claimed to include offline playback of videos, concert footage, exclusive remixes and an absence of ads. Although the price hasn't yet been announced, it's believed to cost $9.99 per month.
Subscribers to the new YouTube Music Key service will also be given a free subscription to Google's other music streaming service: Google Play Music All Access. Confusingly, it's also claimed that Google intends to rename that service "Google Play Music Key."
It has also been claimed that some musicians will see their videos blocked on YouTube after failing to agree with Google over joining the new service. On June 4, indie label music body WIN held a press conference in London to complain that Google was "threatening" and "bullying" music labels into signing up for the service.
Despite a 2013 Billboard report claiming that YouTube's music service would launch by the end of the year, Google has yet to officially announce the arrival of YouTube Music Key. Two high-profile departures have also been linked to the delay: Director in charge of music and paid subscriptions Nikhil Chandhok left his position in 2013, while his successor, Chris LaRosa, exited YouTube last month. The Wall Street Journal reports that both men left YouTube over frustrations with the delay in launching the new service.
YouTube's music streaming service will face competition from Apple and Amazon, with both offering existing subscription plans. Apple's May 2014 acquisition of Beats means that it currently runs two separate music streaming service: iTunes Radio and Beats Music.