Question: John Sebastian is an American-born singer-songwriter, guitarist, harmonicist, and autoharpist,  best known as a founder of The Lovin' Spoonful, that did an impromptu appearance where in 1969? 
Sentence (from "Darlin' Be Home Soon"): It has been described as "...one of the most heartfelt songs about being away from a loved one, written from the point of view of a musician on the road writing a letter."
Relevant evidence: No