I'm not surprised there's a few bands out there you've never heard of. I spent over twenty years in the music industry and at it's peak, including re-issues, the industry was releasing 30,000 albums per year and maintaining an in-print catalog exceeding 120,000 titles. The vast majority of new artists even then faded into obscurity.
Letterman, for the most part, has done an excellent job in showcasing new talent on a consistent basis. Unfortunately, with the decline and splintering of the industry, it's become even harder for new acts to see the light of day and make a living at their craft although new opportunities have presented themselves to those who are well managed and marketed and can build a cult following.
The rapid decline in album sales removed a critical revenue stream from the aspiring artists income so artists have had to become more resourceful than ever before. Sadly, few posses both the talent and the business acumen to make a living creating their art.
I'll stop rambling. Here's a couple of my relatively recent favorite discoveries that I keep coming back to although probably not unknown or even new at this point.
https://www.youtube.com/watch?v=mRUqpgg-8Ps
https://www.youtube.com/watch?v=1vxQs84FMWQ
hehehe, it's funny to think of a 'new' artist being 'broken' by Letterman. I think in a modern context it's more of a 'wow, they were even on letterman!' (or 'this band was on letterman, i think it's safe to say they're old news now).
the internet is everything now. by the time a band has been signed by a label with any kind of profile they're probably going to have sold (or given out) hundreds or thousands of EPs or albums that were self recorded. Music no longer makes its way through Rolling Stone and MTV and times square billboards. Now it percolates with tumblr, music blogs, eventually big review sites like Pitchfork and Stereogum, where you'll see artists who recorded their albums out of pocket in their friend's living room compared favorably alongside albums put out by Sony of bands that fill stadiums. It's pretty cool I think.
There's a gigantic amount of (good!) music that's released on a daily basis. You can find exactly what you want, because somewhere out there there's someone who likes the same thing, and now they have the means to record and distribute it to everyone on earth, without some businessman what and how they need to record to turn a profit.
The latter issue has caused some pretty big label-dropping controversies recently, from the huge self-release of In Rainbows by Radiohead after they got tired of EMI several years ago, or very recently (oh I guess like a year or two ago now) when Sony told experimental hip hop band Death Grips that they would have to wait to release their second album (following up an insanely well reviewed debut album earlier in the year)(Death Grips took the recordings and posted them on the internet, using a picture of the drummer's noodle with the album title written in sharpie on it as the cover art. Just to make sure Sony would never be able to seriously release it).
I think in a lot of cases record labels are more there just as a distributor once the album is already recorded. Of course this may be an idiosyncrasy of the brand of indie/punky sort of music I primarily am into.
Alex G is a good example of an artist who really was touring the country for like a year before his most recent album DSU got picked up by a label. He put out hours and hours of music that was recorded in his bedroom before that.
https://www.youtube.com/watch?v=Zuu44Ka9TEY&index=3&list=RDY9MWgkcggX4http://sandy.bandcamp.com/album/dsuunfortunately you can't download his album from bandcamp anymore since he was signed, you can still stream it though
elvis depressedly is another band in the same vein that I saw with Alex G a few months ago. They haven't released anything through a label yet which is good because it means they can still release their stuff for free. their 2012 album hotter sadness is something i can't recommend highly enough.
http://elvisdepressedly.bandcamp.com/album/hotter-sadness(my bad they're releasing their next album through Run For Cover) (video treats 90s aesthetics as vintage in true cutting edge fashion )(I don't like the direction of this sound oh well)
https://www.youtube.com/watch?v=RmpazNmUHvI&list=RDY9MWgkcggX4Also, what a crazily uncharacteristic St. Vincent performance that was
https://www.youtube.com/watch?v=VDh9bp2y14k
