Code strings show a separate page or pop-up within the YouTube app that encourages users to sign-up for Music Pass - which sounds like a likely name for the service.
It promises offline playback ("take your music everywhere), background listening ("keep your music playing while using other apps"), and uninterrupted music ("no ads on millions of songs").
The no-ads part is the standout clue as to why Music Pass could be YouTube's paid music streaming functionality. Essentially, it sounds like users will be able to build a playlist of music videos, and they will be served those videos without ads. They'll also have the ability to keep browsing around their phone while listening, a feature the current version of the YouTube app doesn't allow.
Google plans to launch the streaming solution by the end of year, Billboard reported in October. It's said to have a free tier with ads, but there was no mention of that in the code found on Wednesday. Billboard says the free route will be the primary way Google wants people to use its service to boost its advertising network.
A similar amount of tracks currently available through Google Play Music All Access will reportedly be available through YouTube's new service. Google is working with record labels to do so.
Google won't confirm the existence of a YouTube music streaming solution. At the moment, we're left to speculate.