Undertone series

An undertone series is like a secret code that only some instruments can play. It's kind of like when you whisper something to a friend, and only they can hear what you're saying.

When we play music on instruments like the guitar, piano, or trumpet, we hear very specific notes that are called overtones. These notes are like the loudest and most important ones that we hear.

But, if we listen very carefully, we can sometimes hear quieter notes that are playing at the same time as the louder ones. These notes are called undertones, and they are like a secret message hidden within the music.

Undertones can be very hard to hear, and some instruments like the trombone are better at playing them than others. But if you listen closely, you might be able to hear some undertones when you play music or sing a song!