YouTube has modified the way it tests new features: it is now allowing its Premium subscribers access to emerging apps in the production pipeline, as first spotted by Android Central. Previously, certain features were tested by Google users randomly selected for beta testing.
Currently, the latest features available for Premium subscribers to try include watching audio videos and searching your YouTube homepage on iOS; voice searching for YouTube videos on-site (only on Chrome); and theme filtering in additional languages. The language at the top of YouTube's experimental features page also suggests that Premium members can only use these features for a limited time.
YouTube Premium costs $11.99 a month and also offers you ad-free streaming, background play, and access to YouTube Songs, among other features. If you're a YouTube diehard, however, limited time access to new features might be worth it.