Me and Atari go way back. My first computer was an Atari 400, and I've owned various Atari games consoles over the years. Nowadays, I'm the happy owner of an 800XL computer named Booxlé.
Occasionally I do something fun with it.
...has its own page
...is a text editor I started to write, in 2009. To my knowledge, it's the only editor for the Atari 8-bit computers which features proportionally-spaced fonts. This is no mean feat. As there's no hardware support for proportionally-spaced fonts, it all comes down to the CPU drawing the characters to the screen. I got it to be usably fast — over 1000 characters per second, which is about what you get on a 9600-baud serial terminal.
I have a disk image with a slightly-borked version of the program, which I'll round-up and post when I can. If I can find the source code, I'll post that, too.
Here are some pictures I've made for and with the Atari computer.
There's a write-up on the creation process for the last image at page H6E.
As far as chiptunes go, I've barely taken a stab at composing anything. In 2015 I played with Jaskier/Taquart's Theta Music Composer 2 for a few hours, and came up with these: