Hum
verb (used without object), hummed, hum·ming. – to give forth an indistinct sound of mingled voices or noises. to utter an indistinct sound in hesitation, embarrassment, dissatisfaction, etc.; hem. to sing with closed lips, without articulating words.
It’s also the what I say to myself as I’m seeing a lot of copyright infringement notices going up. YouTube must have figured out a way to automate their systems to catch them. Here’s a better use of the verb: