Who are they?
Steely Dan are Donald Fagen and Walter Becker.
Why are they underrated?
When I was in high school, I was extremely fortunate to have teachers that gave a crap. My favorite of those teachers was Dr. Coleman, who was my English teacher in both the 11th and 12th grade. He paused at inappropriate times while reading poetry or Shakespeare and he was married to one of the drama teachers. He was always very candid about things that were going on in his life. He pushed us to expand the boundaries of our experience, whether it was in the writing that we did or music that we listened to, or going to check out a play or an exhibit in a museum. He never wrote off the things that we were interested in. He called himself a huge Harvey Keitel fan and didn't laugh at the idea of us playing Sonic Youth records in his class. In a not very interesting coincidence, he and I shared a birthday. In a horrible circumstance, he died of a massive heart attack at the age of 48. He helped shape the kind of person and writer that I am today.
The world that he inhabited seemed like a world that was stuck in the 1970s. He seemed bookish in a Woody Allen way and earthy in a John Denver way. And dear god, did he love Steely Dan.
Who could blame him? Steely Dan are awesome. Their impact is largely forgotten, even though they've recently released a couple of albums (one of which, Two Against Nature, won several Grammy awards) and they're in the rock and Roll Hall of Fame (inducted 2001). Part of this is because the band broke up in 1981 and remained in active for more than decade. Part of this is because they didn't do any touring at all between 1974 and 1993. Part of this is because they're the two ugliest men this side of John McCain and Sarah Palin.
Steely Dan was indicative of everything that FM radio was in its early day (edgy and experimental) and they represent the early days of FM radio: the wild west when it was anything goes on the airwaves because there weren't as many listeners to offend/turn off, as opposed to today's FM radio which is a veritable buffet of crap no matter where you land on the dial. And it's no coincidence that Steely Dan wrote the theme song for the movie FM, about disc jockeys that hijack a radio station when the executives make it clear that they favor advertising revenue over music. They didn't just play on FM radio; they were FM radio.
Their music blends funk, jazz, rock and pop in daring and innovative ways, most notably on 1978's Aja, which shot to the top 5 and was certified platinum within three weeks of its release. And though their music sounds like it's the 1970s incarnate, it's no worse for the wear. It's still incredibly listenable, and since so many people are wearing aviator sunglasses these days (and looking ridiculous in them), it doesn't take much to feel like you're actually in the 1970s. Pop in some Steely Dan, throw on your Toughskins, and rock the fuck out.
Rolling Stone called them "the perfect musical antiheroes for the Seventies." This is an accurate characterization. The guys churned out great music, because they liked to make music. Their fame was just a sidenote.