Music & Science: Pendulums

ENGAGE students

EXPLAIN. “Can you think of things that swing back and forth, back and forth? Chances are you are thinking of some kind of pendulum. A pendulum is a weight of some kind suspended from a fixed pivot (something that doesn't move) so it can swing freely. In other words, if you hang something from a string or cord or rope and let it swing, you've created a pendulum. Pendulums have been used for many things throughout history. They even helped scientists prove how the Earth rotates.”

REFLECT. Look at the diagram below and think about how pendulums work. (Read a little more about pendulums here.)

IDENTIFY. “There are basically two parts to a pendulum–the string, and the pendulum bob, or the weight. Here are some examples of pendulums in everyday life. Can you point to the string (or strings) in each picture? (Hint: in one case, the string isn't really an actual string.) How about the pendulum bob? There might be more than one in each picture.“

EXPLORE sounds

EXPLAIN. “The composer Steve Reich wondered what a pendulum might sound like, so he wrote a piece of music called Pendulum Music. Here is what he did:

• Attached several microphones over loudspeakers

• Hung those microphones from the ceiling, over the loudspeakers

• Asked performers to pull back the microphones, then let them go, so they would swing over the loudspeakers

“When the microphone passes over its loudspeaker, it creates a sound called feedback.”

WATCH. Watch a performance of Pendulum Music. As you watch:

• Think about how the distance each performer pulls back the microphone affects the way the piece turns out. If they pulled them back a different distance, do you think it would affect the sound?

• Notice two performers release their microphones at the same time, and the other two just after that.

• Notice the repetitive patterns that shift slightly over time.
  Once you hear a pattern, try singing along a little. This will help you hear when the pattern shifts.

• By the end, the sound has basically become a drone, or a continuous low humming sound.

REFLECT. “Do you think every performance of this would sound the same?” After discussion, end with: “No, it would never sound the same twice. Many factors affect the end result. What would some of those factors be?”

EXTEND learning

Choose one or more of the following activities to extend learning.

LISTEN. Here is another excerpt of a performance by electronic musician Aphex Twin:

LISTEN. The indie rock band Sonic Youth made a famous recording of the piece. You will notice again that it sounds different than the other two versions.

LEARN. Watch this video that explains the pendulum wave toy.