What gives a piece of music enduring quality?
Consider a few body/spirit/soul analogies. I like to think about…
…craftsmanship as the body of music—counterpoint and voice-leading, proportion and form, treatment of dissonance, and more. “O Worship the King” and “Angels Holy, High and Lowly” contain high levels of craftsmanship.
…artistry as the spirit of music—hard to locate, but of inestimable worth. It is the composer’s fingerprint, sometimes revealed in a melody, or expressed with unorthodox but successful compositional choices. “Now the Day is Over” and “O Love That Will Not Let Me Go” display high levels of artistry.
…sentiment as the soul of music—memories and feelings connected to a song by those who sing them. Sentiment often rests in the hands of good fortune rather than under the control of the artist. Some singing communities have attached high levels of sentiment to “Amazing Grace” and “Just As I Am.”
Songs that lack some of these traits may have limited local appeal for several generations. Artists may be known to various communities, increasing the early success of their work. Perhaps a song was written in response to a tragedy or other impactful event. Tastes of hymn selection committees and song leaders affect congregations and even constituencies. These factors can keep some songs alive for a time. However, songs that enjoy wide appreciation over centuries generally contain strong craftsmanship and artistry, and are often blessed with significant sentimental connections across a broad range of singing communities.