Remembering when........

What is it that clicks those tunes into our minds and, forever after, we can repeat every word with just a note or two intro?
Last evening, Pat (SIL) and her friend, Teresa, and Barbara Jo and myself went to Derby Dinner Theatre for their '8-track - the Sounds of the '70s' show.  From the opening number, Pat was transported back in time.  She lip-synced nearly every word.  She knew "where I was when that was played."  She was alive.  From this, to this, to this, and this.  It was a neat thing to see (and hear!)
Now, my days were the 60s....like this, and this, and this and this.
I think it has something to do with our high school and college days, and first love(s) and such, don't you?