Those of you who have seen Ally Mc Beal would know this. A specific song/ tune repeats in your head when you are in a certain mood.
It gives a feeling of deja vu. More often than not, you will find a few others pick up the vibes and the song.
Nowadays the mood is also set by a song one listens on radio on the way to work.
There are some songs which take hours to get out of your system. The biggest one is "Five Star "refrain in Tamil. In Hindi it is "Excuse me too please" now a days
They are not particularly songs I like, infact they manage to irritate after a while. But they are just like a sticker on your back- difficult to get rid of.
As elaborated interestingly by analogkid:
They are called earworms. i have a few earworm repellants. have to listen to them for atleast 10 mins normally to kill the worms. its a common phenomenon. dream theater's surrounded and any song by tool are my favorite earworm repellents.others picking up vibes part.. i have tried hard to deconstruct it. i came to the conclusion that u either hum it unknowingly which is heard by the other person unconsciously and thus the vibe.. or if u believe in something more supernatural, then maybe its the subconscious minds communicating. :)