The Apple ][ Basic Programming Manual (the "Integer" BASIC manual), written by none other than the late Jef Raskin, has, as you'd expect, a section on saving programs to audio cassette tape (the only form of storage available on the Apple II at the time the manual was written). In that section, the user is invited to listen to the cassette in the same way they would listen to a music cassette. The manual, therefore, contains this all time classic on p. 15:
Quote:
What is it that the computer finds so interesting about these tapes? Listen to one of them. It's not music to your ears. Yet you can recognize some of the sounds the computer listens for. The information starts with a steady tone. Then there is a short "blip" followed by more of the steady tone. The tone is at 1000 cycles per second. This pitch is just below the C two octaves above middle C. After the tone comes a burst of sound rather reminiscent of a rainstorm.
When you are used to the sound of a good tape, you can quickly check a tape by ear to see if it is a computer tape or not. If you can tell what the tape contains by listening to it, you are a mutant, and will go far in the computer world.