The microphone is perhaps the most underrated item on any stage. While guitars, pianos, violins, or the voice get all the attention, without the microphone, they'd barely be heard.
Ever since we humans took the stage, there's been a parallel desire to be heard. This is why actors shouted and why performance spaces were shaped and enclosed to help project the sound into the audience. Simple effects liked cupped hands and shaped cones—sometimes built into the actors’ masks—were as good as it got for thousands of years.
Then, back around 1665, English polymath Robert Hooke devised what became known affectionately as the "lover's telephone." It was a vessel joined by wire or string which, when held taut, could transmit a human voice over long distances. This invention didn't help the public performers of the time, but it demonstrated that sound could be manipulated and amplified.
The first attempts at the electrical amplification of the human voice date back to 1861 when German inventor Johann Philipp Reis developed the “Reis telephone.” In the one hundred years or so that followed, microphone technology—driven by increasing popularity in recorded sound, radio, talkies at the cinema, and the live music booms across Europe and America—leapt forward.
As sound quality improved, the pressure to project was reduced, and singers realized they could sing softly and quietly and still be heard. Out of this new microphone technology—and the burgeoning radio industry of the 1920s—the "Crooner" was born with subtlety and nuance, becoming a fashionable style of performance. Though conservative circles considered this understated way of performing as degenerate, vulgar, and un-American, it became hugely popular.
Over the years, the microphone continued to develop. Ribbon, condenser, wireless, dynamic, uni-directional, transducer, and the electret microphones all offered innovations, improvements, and—for us in the audience—a more enjoyable, more audible experience.
Today, tiny microphones are invisibly buried into our phones, computers, and even our refrigerators and music players. Wherever they pop up next (implants anyone?!), they'll change our listening and speaking lives yet again.