You probably have a song/band/album that is so firmly entrenched in your memory that whenever you hear it you are instantly taken back to a specific time or place whenever you hear it. I've got a few.

Ray Lynch - Deep Breakfast
I have a few songs from this album in my library because they always bring up good memories from my childhood. My parents bought this album on cassette and it was one of the few we took with us to Venezuela, where we lived for four months in late 1985. I can still picture the little boom box we took with us, too. (Hey, I found some pictures of it online!)

My uncle gave my dad a Yanni mix tape and he played it at home occasionally, but what really made Yanni stick in my memory was that we brought it on a 1991 road trip from Southern California to Grand Teton National Park in Wyoming. You can imagine how many times I heard that tape during the drive. The melodic orchestral style really fit the landscape well, though. I do not have any of Yanni's music in my library. Make of that what you will.

Days of the New
Their first studio album, in particular, takes me back to the living room of the house I rented in college, with the dingy off-white couch arranged diagonally across the room from the TV and sound system, all on an equally-but-perhaps-more dingy brown carpet. Ken (kcarlile) and I lived together then, and he had these speakers he'd upgraded with Radio Shack-sourced components attached to some ancient Marantz receiver. We played this album often, and loudly.

EDIT: Last minute addition.

How could I forget Yes - Union
My sister had this tape (which she dubbed off our uncle's CD) in her gray Mazda for many months (along with They Might Be Giant's Flood -- but that album's so ubiquitous it isn't associated with any particular memory). She was a senior when I was a freshman in high school, and she often gave me a ride to school.

So, tell me what's on your instamemory music list.
I can explain it to you but I can't understand it for you.