Don Williams would have turned 81 this year. Revered as one of the finest singers of the genre, the “Gentle Giant,” who died in 2017, was known for his smooth, mellifluous vocals. Listen to his sublime phrasing in the 1980 country Number One “I Believe in You,” an Adult Contemporary crossover hit as well. That song, and nine other equally marvelous recordings, make up Williams’ 5 essential tracks.