1.Take notice - perk up you ears mentally
2.You must identify the song at least title. For some of us we MUST name artist and if at all possible year too (this could be in your head or outloud - depending on who you are with)
3. Go back to what you are doing as if nothing had happened.
The whole sequence may take a split second or a couple of seconds but there you are staring off into space for a moment as your brain tries to pull out that saved music file from the music library in your mind. I thought it was only me but I was sitting in a diner the other week with the kids and the dh and I actually saw that look on his face. He had been in the middle of a sentence about I don't remember what but he stopped, looked up towards the ceiling and then said "Rock the boat" which I answered "Hues Coorporation" and then he finished his sentence. We laughed that it tends to be a contest with us but that time he got that eye-looking away face so I called it a music "moment". I have been known to do this many times. But now it has a name.