Back in the early days
of digital computers, engineers would often troubleshoot hardware by
writing "musical software." Portable AM radios would be used as "sniffers"
in circuit areas where tubes and/or relays would be turning on and off
with rhythms that were determined by the test software. If the chosen
familiar tune did not sound as it should, then the problem could be
deduced to be associated with that area of the processor known to be
controlled by the program.