Question: What is a compilation album of previously unreleased songs and alternate takes recorded 1969–1980 by American singer-songwriter, who was one of the most popular acoustic artists of the decade and one of its best-selling artists?
Sentence (from "John Denver"): By 1974, he was firmly established as America's best selling performer, and AllMusic has described Denver as "among the most beloved entertainers of his era".
Relevant evidence: No