Yokee draws from YouTube to curate a list of instrumental YouTube videos so you can enjoy free karaoke on your iPhone. Combining a number of tools, including recording, a search function, and quick playback, you can do quite a bit with this app. Onscreen lyrics, edits to the songs, and changing beats and tempo are not available because the app uses YouTube videos; but for a limitless supply of popular songs, you can't beat its catalog.
While you can choose to link your Yokee app to Facebook, it is not necessary, so the app works fine without any log-ins. It immediately shows you all of the top videos currently on YouTube as curated by the app's developers. Each video is an instrumental of a popular song with lyrics, allowing you to sing along. The app will record as you sing and play it back later if you choose to listen. The only issue with this is that you need to know the song fairly well or you won't be able to match the tone of the song well since lyrics flash onscreen but aren't metered to the music. The search interface and display mode are all very well done, however, so if you do know the lyrics, this is a fun app to use.
While there are certainly more powerful, feature-rich karaoke apps on the App Store than Yokee, they almost all cost money to use, especially for popular tracks from top artists. With Yokee, you may lack some of those more powerful features, but your library of songs is much larger.