Sunny and uplifting are not words generally associated with Willie Nelson, but that’s not the only reason some will be surprised by his new album. Organized loosely around duets with younger stars and a Cyndi Lauper cover, The Great Divide is glossy, tuneful and turned up to ten — which would constitute a triumph for another artist. But Nelson is a performer who uses plain, powerful lyrics and a handsome but unvarnished voice to great effect. Much of that gets lost in the adult-contemporary production goop and heavenly choirs of “Be There for You” (Sheryl Crow is in there somewhere as well, but you wouldn’t know it). In the same vein, the sheer bathos of both his duet with R&B schmaltz king Brian McKnight and the gunslingin’ ballad featuring Kid Rock overwhelms Nelson’s talents. The superbly hummable “Mendocino County Line,” written by that old ranch hand Bernie Taupin, is better, pairing Nelson’s crooked and rusty voice with Lee Ann Womack’s honey-covered chirp. Ironically for an album that may be a nod to Carlos Santana’s collaborative smash Supernatural, the best moments here are the ones in which Nelson just does his thing all by his bad self. On the menacing, swaggering mean-man shuffle of “Just Dropped In,” he croons like a philosopher-poet who has been poisoning the well at Leonard Cohen’s ashram. And the troubled Spanish acoustica of the title song makes it clear Nelson never needed the young blood that appears elsewhere on the record: Nelson’s sound is so deep, so sad yet unapologetic, that he can make a lyric about the summer sun seem as dark and cold as a meditation on the Arctic.