incredibox.com* - A platform where you can create your own music beats. You can create fun and creative tracks by combining different characters.
radio.garden - This site lets you listen to radio stations from all over the world. (Even I was listening as I wrote this.)
www.patatap.com* - A very enjoyable site, both visually and audibly, where you create sounds and animations as you press the keys on your keyboard.
musicgpt.com - This site is ChatGPT as you know it, but with a focus on music.
strudel.cc - This site lets you create music using the power of codes. You might not find much on the homepage, but if you go to strudel.cc/examples, you can pick any song and listen to beautiful music created with just a few lines of code. (If you're a programmer, this site is great.)
musiclab.chromeexperiments.com/Song-Maker/ - As the name suggests, this is a music maker. There are squares everywhere, and they represent individual notes. If you fill them all in neatly, you'll have beautiful music! (This is my suggestion; even random notes can be beautiful.)
Music lab demo (press the play button at the bottom)
* Fun
This category contains some fun links, even though it's in the Functional section, because there are so few fun sites that it wouldn't be worth opening a new fun category specifically for them.