There have long been rumors that Google (S GOOG) is planning to launch a separate music subscription service for YouTube, and it looks like those plans are now starting to come together: The folks over at Android Police found a number of references to something called “Music Pass” in the latest Android YouTube app.

A file called music_upsell_dialog.xml contains text strings that promise offline playback to “take your music everywhere,” background listening to “keep your music playing while listening to other apps” and uninterrupted music with “no ads on millions of songs.”

A YouTube spokesperson declined to comment on these specific findings, and instead send me this statement:

“We’re always working on new and better ways for people to enjoy YouTube content across all screens, and on giving partners more opportunities to reach their fans. However, we have nothing to announce at this time.”

Google is already running a Spotify-like music subscription…