The track selection ranges from show tunes, chart hits and karaoke classics like New York, New York and I Will Survive, to hip hop, soul, R&B, rock, indie and brand new pop tracks from acts including Hurts and Owl City, as well as kids songs and film soundtracks. Helpfully (?) it gives you the key at the start of each track and check out the excruciatingly twee background videos too.
I came across this option by chance and it seems not many of the other Virgin users I know were aware of it either so I hope this is good news for at least some of you.
You can choose your aural posion via genre or browse the whole menu. Personally, I've never done karaoke but being able to practice in the privacy of my own home might just change that...
To access: From your Virgin Media TV remote (which you can also use as a microphone, hairbrush style), press the Home button, select On Demand & Catch Up TV, then Music On Demand et, voila! Karaoke.
NB: PLEASE check if you have to pay to use this service before running up any massive bills!! :) It says it's currently free if you have an XL package but best to be on the safe side. Phew.