Once I returned to the states I learned it was by CSN&Y when I called up a local radio station to ask that it be played. They didn't play it, but I learned the name of the band, and bought myself the album.
I still stop dead in my tracks and get warm all over whenever I hear it played on the radio or over a speaker at a store. When I hear it at home I smile and have a sudden urge to let our two indoor cats into the backyard, throw some flowers in a vase and light a fire in the fireplace. (I don't really let the cats out)
Once Cindy and I got into a pretend argument because we wanted to claim that song the song of our present lives.
Here's a YouTube video of the song. (edited because the original video is gone)
Edited to add this interview by Graham Nash explaining the song. (thanks Del!) I love it when something I love is explained. It makes it so much better. Usually. I love a good steak, but don't want to know that much about it.