Some that I think should be wayy more popular than they currently are:
- Jukebox the ghost
- aimee mann
- V.A.S.T
- Prefab sprout
- Ivy
- Passion pit
- Placebo
- The war on drugs
- tokyo police club
- Stars
- The dismemberment plan
I'm not familiar with most of these but I drove 2 hours to see Jukebox the Ghost play in the second story of a church when I was like 19, and Stars is probably my number one favorite band, so I may have to check out some of your other entries here.
Edit: The Jukebox the Ghost show was really cool btw, they wouldn't let them do an encore in the upstairs part of the venue but they agreed to let the keyboardist do a solo encore on the church's organ on the first floor.
I saw them twice live, they're so good. Not many bands have the same optimism and energy as they do.
Probably, I don't know how I found them but I grew up in the 90s and 00s and never heard of them.
Sleep Token. They're not as obscure as they used to be. They kind of blew up this year but only in the metal scene. Not quite mainstream yet but I think they'll get there.
Fuckin love umph, got to see them twice so far. Once with sts9, which I also love.
Here's a few sludgy/doomy metal bands I've been listening to a lot lately: Froglord, Squalus, GUHTS, Grayceon, Hippie Death Cult
Also I think he's starting to breach mainstream popularity, but I'd be remiss if I didn't spread the word of Amigo the Devil (dark country/folk, "murderfolk")
Atomship. It was a blend of alternative metal and progressive rock. It's a really unique sound and they only ever did a single album.
They're not really considered underground since they have 1 million monthly listeners, but I still don't see a lot of people talking about the band Foreign Air. They are known for their hit "Free Animal", but they have so many good songs. I recommend "Your Touch", "Hello Sunshine Pt 2", "Wake Me Up", "Moving On," and "Monsters". Unsure of how to describe their genre, it certainly isn't rock nor bubbly pop...
Collective Soul (fairly popular in their heyday, less so now)