Brains On! Science Podcast for Kids

Episode: How does music get recorded and stored?

Air Date: November 25, 2025
Host: Molly Bloom
Co-Host: Canyon from Montreal, Canada
Special Characters: Robot who only eats physical media, Mark, Sandon

Episode Overview

This episode dives into the fascinating world of sound recording and playback. Molly and her kid co-host, Canyon, explore how music and other sounds make their way onto records, cassette tapes, CDs, and digital files. With help from their friends—a goofy robot obsessed with physical media and the all-poodle heavy metal band “Penelope and the Poodles”—they shrink down and “surf” sound waves, unraveling the science and technology that lets us capture and replay our favorite tunes.

Key Discussion Points and Insights

What Is Physical Media? (03:15)

• Physical media means music and sounds stored on something you can hold—like a record, cassette, or CD.
• Robot who only eats physical media gives playful, food-themed descriptions:
  • CDs: Shiny, flat discs with a hole in the center—“like a bagel.” (03:27)
    • “They play about 70 minutes of music. Again, like a bagel.” (03:59, Robot)
  • Cassettes: Small plastic rectangles with spools of brown magnetic ribbon—“delicious,” says Robot. (04:37)
    • “Inside the cassette, there is a spool of brownish ribbon, kind of like a really thin roll of tape, but not sticky.” (04:41, Robot)
  • Vinyl records: Large black discs with grooved surfaces—Robot’s “dinner.” (05:16)
    • “If you squint your robot eyes, you’ll see that records are covered in tiny grooves... that is where the music is stored. It’s also where the flavor is stored.” (05:41, Robot)

How Does Sound Get Recorded? (07:30–08:00, 11:00–14:10)

• The basics haven’t changed in 150 years: someone plays music, the sound goes into a microphone, and is saved on a recording device (tape, computer, etc.).
• Sound waves: Vibrations in air that our ears (and brains) interpret as music.
• Children’s analogy: Shrinking down to surf a sound wave, following how it travels from instruments to our ears.

Microphones: Turning Sound into Electricity (17:49–20:06)

• Microphone’s diaphragm: A tiny plate inside a mic vibrates in the same pattern as the incoming sound waves—like a machine version of our eardrum.
  • “Think of the inside of a microphone like a machine version of your eardrum. It’s listening to music...” (18:24, Mark)
• This vibration is turned into a pattern of electricity.
  • “It’s wild to me that sound can be turned into electricity.” (20:02, Molly)
• Key concept: The same pattern (the “code” of the music) gets transferred in different forms along the way—sound wave, electric current, digital code.

Storing the Code: From Electric Signal to Tape, CD or Digital (21:11–22:24)

• Analogy: The “master file” of a recording is a new kind of code, still with the original pattern.
• In old systems, electrical signals are stored as a code on tape; now, they’re turned into digital files computers can read.
  • “...that pattern from the waves of air is turned into different codes. Sometimes it’s electric code, sometimes it’s digital code, but it’s always the same pattern.” (20:47, Mark)

How Do Speakers Work? (24:18–25:02)

• Speakers reverse the microphone process: they turn the electrical code back into a moving plate (speaker diaphragm), which vibrates air back into sound waves.
  • “Inside a speaker, there’s another kind of plate like the one we saw on the microphone. The electrical signals make it wiggle in that same pattern as the original sound. And as it wiggles, it pushes on the air around it, creating sound waves.” (24:20, Mark)

How Different Media Store Sound (23:23–25:50)

• CD: Digital code is written onto an aluminum disc; a laser reads this code and turns it back into electrical signals.
• Cassette Tape: Musical code is stored magnetically on a ribbon inside the cassette. Tape players read the magnetic code, turning it back into electricity.
• Vinyl Record: Sound is stored as tiny bumps and grooves. A needle rides along these grooves to recreate the music pattern for the speaker.
  • “The music’s code is stored as little bumps inside those tiny grooves. A very small needle rides on those grooves. As the record spins, the needle helps turn that code back into an electrical signal which goes to a speaker...” (25:14, Robot)

Notable Quotes and Memorable Moments

• On physical media formats:
  • “They’re shiny, flat discs about 5 inches wide, like a bagel. They have a hole in the middle, also like a bagel. And they play about 70 minutes of music. Again, like a bagel.” (03:36–03:59, Robot)
• On sound waves:
  • “We’re so small now we can surf a sound wave. Sound waves are how sound travels.” (13:36, Mark)
  • “The waves of air are making that diaphragm plate thing vibrate and wiggle in a pattern too.” (18:10, Molly)
• Microphone as electric translator:
  • “Microphones just take that same pattern and write it as electrical pulses.” (20:06, Mark)
• On digital vs. analog:
  • “The pattern was like a code? The same information, but stored in a different way?” (20:41, Canyon)
  • “Yes, yes, yes, yes, yes, exactly like code.” (20:47, Mark)
• On the chain from recorded sound to your ears:
  • “The speaker wiggles the air to make sound waves. Then your ears hear those sound waves, and that’s how you hear music.” (26:46, Molly)
• Robot’s parting wisdom (and appetite):
  • “The important part is that you thoroughly chew your record so you don’t choke on ‘Look What You Made Me Do.’ Taylor’s version really does taste better.” (25:32, Robot, jokingly)

Timestamps for Major Segments

• Physical media explained (CDs, tapes, records): 03:07–06:20
• How recording works, in a nutshell: 07:30–08:00 & 11:00–14:10
• "Shrink adventure" inside a sound wave: 13:23–14:40
• Inside a microphone—how sound becomes electricity: 17:49–20:02
• Turning sound into code, storing in computers/tapes: 21:11–22:24
• How speakers turn code back into sound: 24:18–24:43
• How different formats store music: 23:23–25:50
• Summary wrap-up: 26:27–26:59

Bonus: Mystery Sound (08:11 & 27:36)

• Mystery sound played and guessed: 08:11 (Canyon guesses trailer; Molly guesses campfire pan)
• Answer revealed: 28:13
  • “Hello, my name is Sophie from Arlington, Massachusetts. And the sound that you just heard was me opening and closing the flue of my fireplace.” (28:13, Sophie)

Episode Tone

Fun, light-hearted, silly, and packed with analogies. The robot character delivers playful, food-based riffs on old music formats. Molly and Canyon are relatable, honest about not always knowing the answers, and make learning about complex science fun and accessible.

In a Nutshell

• Music is a pattern of air vibrations (sound waves).
• Microphones turn those vibrations into electricity, stored as analog or digital code.
• That code can be pressed, magnetically imprinted, or encoded onto physical media like records, tapes, or CDs, or saved as digital files.
• When played, speakers reverse the process, turning the code back into sound waves your ears can hear.

The episode blends science, silly characters, and hands-on curiosity—making the technology behind music recording and playback come alive for listeners of any age.