Always thought it was a Carpenters song but all credit goes to the rock group Klaatu. I had never heard of them, but I am not very familiar with Canadian progrock either. The cover version by Babes in Toyland comes from a Carpenter tribute record. Are you still with me?
Babes In Toyland - Calling Occupants Of Interplanetary Craft
If I Were A Carpenter - 1994