when hearing a bit of Atari Lynx music today, i thought to myself, “huh this mostly sounds like Sega Master System music, where it’s all just square waves, but it’s a bit more complex than that. what actually is this console’s sound chip?” Wikipedia just says “4 channel sound”, but further searching turned up an AtariAge forum post that described it as such:

It has a form of a linear feedback shift register (or LFSR) random number generator that has a length of 12 bits.
Bits 0-5, 7, 10, and 11 can be feedback taps. Each bit also has an output gate to XOR feedback.

It was time-consuming for composers to get a decent waveform out of the LFSR synthesizer, so they just kept one feedback bit enabled, in which generates what is called "pure square waves". That's why most games tend to sound like a "Master System" at times.
The chip also had a mode for "integrated" output, which is just a form of random DPCM instead of raw noise. This just changed the amplitude of the DAC up or down over time. This would've been easier for "flute-like" sounds of those composers, as they can possibly simulate a triangle wave.

The DACs also had a register for streaming 8-bit PCM audio. Klax and Qix are currently the only games I know that used PCM music.

this sounds absolutely buckwild for a sound chip design! i struggle to imagine how one would wrangle these synthesizers into doing reasonable‐sounding things. and yet, today i also found a new favourite obscure tune of mine by someone who managed to do just that within this console’s brief lifespan (though apparently this game went unreleased until 2004!), which i want to share:

Something I posted over on kbin, aka "carob Reddit." Yes, Chip's Challenge is back, in Switch form. Yes, it's one of the hardest damn puzzle games you've ever played. Despite his intense Urkel-level nerdiness, Chip makes Lolo from Adventures of Lolo look like a fuzzy blue wuss.

This Halloween's game is Dracula the Undead, a technical showcase for the Lynx that adapts Bram Stoker's novel into the adventure game format. An adventure game on the Lynx? It's more likely than you may think!

Dracula the Undead is a serious technical feat on the Lynx. Take a look at some screenshots or watch a video and you'll see some of nicest visuals and atmosphere you can get on the platform. It uses lighting and sprite scaling in ways that create a mood and feel unheard of on the platform It's really cool! Dracula is also a fascinating oddity on the console, being the only adventure game to release on the Lynx. It seems like a recipe for an interesting but overambitious experiment, and sure enough, that's pretty much what you get.

Despite the excellent presentation, Dracula the Undead is as straightforward as adventure games get. You walk around, find items, use said items, and try to figure out where to go. There's nothing wrong with the formula, but likely due to limitations of all kinds (since it's a Lynx game, you can't even save!), there just isn't much about Dracula that makes it interesting beyond its presentation. There's little in the way of dialogue (though it's a lot for Lynx standards!), the puzzles never evolve beyond fetching items, there are only a couple of spots where you can lose and they're easily avoided once you know about them, and a large portion of the game is spent climbing along a wall in the slowest, most agonizing fashion possible. What's supposed to be a horror experience ends up being anything but because once you see the lack of mechanical/scenario evolution over the course of the game, the only threat that remains is having to climb that accursed wall again. Still, even though it's not a great experience at all, if I'm being frank, Dracula the Undead is absolutely worthy of respect just for how truly singular it is on its platform of choice, a fascinating little historical footnote for the Lynx if there ever was one.