More on the SETI sound sample:

The data are one of the samples provided by setiQuest to help the community develop new analysis techniques. (More about this in Jill Tarter’s TED wish.)

The data themselves are from a pulsar B0329+54 which is the strongest pulsar in the sky. It seems appropriate to use a pulsar, since LGM-1 was a nickname for the
first pulsar to be discovered.

The sampling frequency of 8.73813 MHz which is 15 octaves above middle C (plus a third of a semitone to be precise). Jonathan has averaged the signal in blocks of 2^17, effectively transposing by 17 octaves. You can then hear a rumble like the lowest note of a cello, with the heartbeat-like pulses of the pulsar beacon.

Paul Bourke at the University of Western Australia illustrates other ways of sonifying a pulsar.