Hitting That Golden Note...

NASA - Gold Record on Voyager spacecraft

"In the upper left-hand corner is an easily recognized drawing of the phonograph record and the stylus carried with it. The stylus is in the correct position to play the record from the beginning. Written around it in binary arithmetic is the correct time of one rotation of the record, 3.6 seconds, expressed in time units of 0,70 billionths of a second, the time period associated with a fundamental transition of the hydrogen atom. The drawing indicates that the record should be played from the outside in. Below this drawing is a side view of the record and stylus, with a binary number giving the time to play one side of the record - about an hour."

"Things that make you go: hmm..."

That's assuming our aliens still have something like a record player with a stylus. (For me), I'm afraid my father's collection of Nate King Cole albums (to date) remain unplayed. I bought the CD.

NASA: Voyager Golden Record