Peer in through the parlor window at a piano teacher's house on a Thursday afternoon in 1945. A young man sits at the piano bench practicing scales. Above them both, resting on the piano top, a metronome ticks and tocks back and forth, its pendulum scraping the air like a tireless windshield wiper.
Patented in 1815 by Johann Maelzel, the metronome is an instrument used to keep time for music. Maelzel's metronome used an escapement (think of the toothed wheel that makes a watch tick) to transfer power from a wound-up spring to a weighted pendulum. Each swing of the pendulum produced an audible tick, and users could adjust a dial to control the tempo of the ticking [source: Underwood].
Pretty soon after its invention, notable composers such as Ludwig Van Beethoven began including metronome markings (beats per minute notations) on their manuscripts [source: Rockwell]. Musicians had already adopted standardized symbols to indicate time signature, key, dynamics and note relationships. In the same way, metronome markings were a way for composers to communicate the tempo at which they intended a piece to be performed.
Think of a metronome as graph paper for the ears. By imposing a tempo grid over a piece of music, students are able to break down complex polyrhythms into smaller, more comprehensible sections. They can then practice these difficult passages at slower tempos, gradually increasing the tempo as their technique improves. The steady, constant ticking of a metronome also helps students identify when they're unconsciously speeding up or slowing down sections of music.
The first metronomes were spring wound and, like old watches, they tended to keep time poorly as the springs lost tension. Today's metronomes are more reliable. Some can even be programmed to play a variety of sounds, from conga drums to electronic cheeps and beyond. Head over to the next page to read all about how different kinds of metronomes work.