Start with different people talking all at once - some loudly, some softly. We can try and make out what someone is saying, but it's not easy. So we put each person on a different radio station & we then 'tune' our radio with a little knob and dial.
If our ears could hear radio frequencies - like AM1070 - then each station by itself would sound like a dull drone or a tuning fork. It's dull because it's repetitive - it sounds the same this second as it sounded the previous one. To make the drone interesting we multiply it with a person's voice signal (say from a microphone or rolling tape) - then the drone kind of goes wah-wuh-wuh-wah, and this 'modulated' signal is a lot more interesting.
That's basically the Fourier transform - a sum of Speech.Station signals, where Speech is interesting and Station is repetitive.
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We can play this same game with the speech itself - or music. Think of each note do-re-mi-... as radio stations, and the pressure applied to each key of the piano as the speech. So, music can be represented by a combination of the form KeyPressure.MusicalNote. The KeyPressure sequence can be recorded in a music sheet. The notes themselves are boring (as the kids say in The Sound of Music, the notes don't mean anything), it's the "multiplication and sum" with the KeyPressure sequence that makes music.
Again, note the summation overy x.y terms, where x is interesting and y is repetitive - that's the Fourier transform.
Historical sidelight:
The simplest sheet music is Morse code, dah-dit. When telegraph became a booming business there was a shortage of wires to handle the volume of messages. People wanted a way to send more Morse per wire. Alexander Graham Bell had a bright idea - this was a few decades before radio - he took several Morse streams & put each dit-dah-dah-dit-dah sequence onto separate notes (like do-re-mi), and then sent the lot down a single wire. As he played with his system he had the deep insight that if the Morse code was replaced by sheet notation, then he could transmit music down a wire - and that became the telephone!