Looking for karaoke software.  

Actually there is a way you can do it! My daughters sing together for weddings, at church etc. A couple of weeks ago, they were asked to sing at a family reunion. My grandmother wanted a specific song too! "The Climb" from Miley Cyrus. We didn't have time to order it and never could find it in a store.
Then about three days before the event, when they thought they were going to have to do something different. The youngest one found the karoake version on YouTube!

Now, they couldn't download it, but what they were able to do, is pull it up. They left the window open even after disconnecting from the internet. Then they just hit play, and the song started. I don't know exactly what you're looking for, or even if this advice will help, but thought I would offer it anyway!