“Rock and Roll All Nite,” Kiss.
Wow, I’m suprised we have gone so far through a thread and no one has come up with the right answer (although a lot of good choices).
The most 70s feeling song ever is Fly Robin Fly. It came out when I was 13 and I remember thinking “is that all there is to it?”. The lyrics are suprisingly easy to memorize.
damn chicklet keyboard!
You Sexy Thing by Hot Chocolate has got to be right up there.
Sammy Johns - Chevy van
This one just gobsmacked me. Joy - Apollo 100
Let’s see: I want a singer/songwriter’s semiautobiographical story-song, but make sure to (a) throw in a section with super-high falsetto, and (b) dwell on flying so hiiiiigh when I’m stoned; there’s a wild-man wizard hiding in me, illuminating my mind – oh, and figure the guy doesn’t get the girl in the end, plus kick the whole thing off by mentioning “Frisco”, with bonus points for working in just how far a buck went in the '70s.
TAXI, by Harry Chapin.
I nominate “Freedom of '76” by Ween: topical, soulful, falsettoy, and written waaay after 1976.
Also, the “modern rock meets white eyed soul” sounds of Heavier Things by John Mayer and Wood/Water by The Promise Ring. I know I can’t listen to those albums without thinking of the 70s.
The other day on the radio someone (Mike Rhyner, a noted old coot) misquoted the lyrics to this as “I wanna rock and roll all night, and part of every day!”
Like, the next day he was too tired, so he only wanted to rock and roll* part of* the day. The rest was, what? a nap? 
Thanks for this thread. Now I have Me And You And A Dog Named Boo looping in my head.
Oooh. Good call.
How about http://www.youtube.com/watch?v=R5Wpn3dFrEs Shannon, by Henry Gross? It’s got some of the elements — semi-autobiographical, maudlin, falsetto, … hell it’s about a pet dog drowning
Loving you…is easy 'cause you’re beautiful…doot n doo doo doo dooooo…<makes noise only dogs can hear>
I thought I had buried that one deep enough into my subconsious mind but you had to go and recover it! Her voice could break glass.
Leo Sayer You Make Me Feel Like Dancing
Listening to a few 70s songs last night, Irealized I’d have to put in a vote for “I Got a Name” by Jim Croce.
And Harry Chapin’s “Taxi” gets a vote too.
We’ve got so many different answers.
The truth here is obvious: the 70s were all over the map, musically, socially & politically.
No one song from the era defines the era.
Humping
I’m not in love by 10cc was the first one that popped into my head.