GUNFIRE - THAT'S MAGUS NIGHT -Rampageous Shooting Star-
Many lines of code were written listening to the whole circle's music on a loop for N days straight. Entire decoders, in fact.

Amateras Records - Purely
Amateras are a solid and well known circle. They're less house-orientated than Alstroemeria but they'll occasionally do something like this.

全自動少女 - モダンガアル街を往く。
Made of a few members of the <echo> project circle they released one great album in 2012, then failed to get a seat at an event IIRC and released one already-made song on their soundcloud before splitting.

Sound Online - 春暁ストライド
Okay albums with a few hits, impressive cover art.

Marginally related, Diverse System's AD: HOUSE series are my favorite as far as doujin things go, though they're pretty much an indie label that happens to go to M3 and Comiket and organizes joint albums like these.
Yes, that's cover art by Mika Pikazo. Yes, I own all AD: HOUSE albums, some still unwrapped because I bought them on bandcamp too. And the artbook. And tshirts which I won't wear like ever. And clear folders which weren't even sold!
Yes, that's the classiest house music made.

SWING HOLIC - 春のざわめき
They do jazz and occasionally big band. Comfy to listen to.

Hatsunetsumiko's (発熱巫女~ず) - Blooming Nights.
Consistently making good albums and still active. Some tolerable engrish. DANCE with WOLVES is more upbeat and groovy but not in the mood for it now.

The is 1.5TB of music by 1.5k circles with almost 10k albums. Dive into it searching for good music and you'll find some gems. Will be posting some occasionally under this tag.
This is Attrielectrock - Well [ATTRi mix]. They made 2 extremely good albums like this and 1 cafe-themed that I think are worth a listen.

Parsee

A Mastodon instance for people interested in multimedia, codecs, assembly, SIMD, and the occasional weeb stuff.