Seventy years ago, the March 1956 issue of Radio Electronics showed this idea, sent in to the magazine by one Jess Jacobson, of how to turn a 5-tube radio into a metronome for the aspiring musician. A few components, including a neon lamp, are simply added to the radio to form a relaxation oscillator from the final audio stage. An RC circuit charges up until it is able to light the neon lamp, at which point a click is heard in the speaker of the radio, which has been tuned to a blank spot on the dial.