Unknown song stuck in your head? Hum it to Google.

If you've ever had a song stuck in your head but didn't know the words or the artist, you know it can be an all-consuming mission to name that tune.

You're hard-pressed to search for it when all you know is the chorus goes something like, "Hmmm, hmm, hmm-hmmm, dunnnn..." Yeah, that's not searchable. 

But as of Thursday,...