This clock maps the twelve divisions on a clock to the notes of a twelve-tone scale, allowing you to hear the current time as musical intervals.
First, it plays a low A to establish a baseline. Then, it plays the note corresponding to the hour (A=12:00, B♭=1:00, B=2:00, and so on). Next, plays the note corresponding to the most recent five-minute interval (A=:00, B♭=:05, B=:10, and so on). It repeats that minute-note between one and four times to indicate how much of the current five minute period has elapsed. (Once means the period has just begun; twice means a minute has elapsed, and so on.) In this way, you can hear the current hour and minute exactly.