This picture shows the inimitable Glenn Miller shaking hands with a clarinetist and illustrates the fact that not only Glenn Miller but the clarinet itself always reminds me of my dad. Apparently the key to the Glenn Miller sound involves a clarinet.
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.