George and Ira Gershwin had a routine. George would write the music, then play it, with Ira sitting behind him scribbling lyrics. But the song "(Our) Love is Here to Stay," was the tragic exception—George died of brain cancer at 37 before it was finished, and Ira was left to complete it on his own. He wrote:

     In time the Rockies
     may crumble
     Gibraltar may tumble
     They’re only made of clay
     But our love is here to stay.

The literary scholar Morris Dickstein reported in Dancing in the Dark: A Cultural History of the Great Depression that the song, which premiered in 1938, was "part of the music of time that soothed the spirits of the Depression years; a sense that life was transient, even catastrophic, but that a core of grace, remembrance and connection survived."

Minus the Depression reference, Dickstein could hardly have written a better description of the role of the Psalms over the millennia. Hundreds of years B.C.E., an ancient Israelite wrote of Jerusalem:

     Therefore we will not fear, though
     the earth should change,
     Though the mountains shake in the
     heart of the sea;
     Though its waters roar and foam,
     Though the mountains tremble with
     its tumult. 

That's Psalm 46. Ira Gershwin may not have claimed it as inspiration, but it seems likely, especially when it's paired with a quote from the Book of Isaiah: "For the mountains may depart and the hills be removed, but my steadfast love shall not depart from you."

The difference between the two lyrics is that whereas the love in the psalm is the love of an all-powerful God, the love in the song is human. Yet the Gershwin works just fine.

The song and its place as an American standard are a robust indicator that non-believers can find a lot to love in the Psalms. The country's fastest-growing religious category, according to a recent Pew Research survey, remains the religiously unaffiliated. During the White Light Festival they, like the "spiritual but not religious" and "just plain unbelievers," and others whose faith doesn't happen to involve the Judeo-Christian God, will have a marvelous opportunity to hear choral music based on all 150 psalms. But are they allowed to consider it marvelous? Can they attend in good un-faith? Or are they cast out of the choral garden for lack of belief, relegated to wander soberly through the groves of more secular musical fare?

A first glance at the Psalms suggests that they might be excluded. Few biblical books are more God-drunk than the Psalter, the flotilla of 150 poems anchored halfway through the Christian Bible, and about two-thirds through the Jewish Tanakh. The Psalms find so many creative ways to invoke God that evangelical pastors sometimes break the Bible-class ice by challenging the room to name them all (there are 33, according to one website: "My shield," "My rock," "My light and my salvation," etc.). The Psalter is one of the great monotheizing literatures, written as Israelite belief was becoming Judaism and moving from henotheism—where our god is the best god—to monotheism, where God is the only God. The energy of that realization pulses through the book.

The Psalms are exotic yet familiar—exotic because they are the literature of a fiercely reverent desert tribe 2,500 years ago; familiar because through historical accident, that tribe's thought structures are baked into our own.

Yet even before the final Psalm's completion in the fourth century B.C.E., and certainly since then, the identity of the figure at the collection's center has turned out to be surprisingly malleable. A few psalms may originally have been hymns to the Ugaritic god Ba'al. For about a thousand years the God of the Psalter was exclusively Israelite and then Jewish. Then the writers of the Christian Gospels put several of the Psalms up in lights—but as part of a very different show. Thus "My God, My God, why have you forsaken me?" the first line of Psalm 22, is better known to Christians as Christ's cry from the cross. By the time the Psalms dominated Christian liturgy in the early Middle Ages, each one could be read either as Christ's words or a prophecy about him. Reformed Protestantism revived them as a history of the Israelites—but as prototypes for Calvinists.

So there's literary-historical license to interpret "God" in the Psalms as one sees fit: everyone else has done it. In other eras that might not have prevented you from getting excommunicated or burned for it, but today we enjoy, atypically, a religious free market. The only question is, are they worth the spiritual and intellectual effort? To which, the answer is also yes.

First, the Psalms are beautiful. Ancient Israelite poetic structure differed significantly from today's, but its use of metaphor remains ravishing in any translation, as when Psalm 19 declares, almost hallucinogenically, "The heavens are telling the glory of God; and the firmament proclaims his handiwork. Day to day pours forth speech, and night to night declares knowledge. There is no speech, nor are there words; their voice is not heard; yet their voice goes out through all the earth, and their words to the end of the world."

The Psalms are exotic yet familiar—exotic because they are the literature of a fiercely reverent desert tribe 2,500 years ago; familiar because through historical accident (or divine providence), that tribe's thought structures are baked into our own. The Psalms' interiority, for instance, is the godparent of autobiography: it was between two series of sermons on the Psalms that St. Augustine wrote his Confessions, which begat Romantic poetry, which begat The New Yorker. It's difficult to imagine Shakespeare writing Macbeth's grim "Tomorrow and tomorrow and tomorrow" soliloquy without his Bible open to Psalm 90: "For a thousand years in thy sight are but as yesterday when it is past...our days are passed away in thy wrath: we spend our years as a tale that is told." Dante ran psalms through his Purgatorio as they are ordered in the monastic hours. Phrases from the Psalms crop up in English like moraines of a poetic glacier: "Down to the sea in ships." "Make a joyful noise." "Out of the mouths of babes." "Hallelujah." The 150 choral settings presented in the White Light Festival make up a tiny fraction of all the music and art the Psalms have inspired over time.

Next there's that voice. Aggressive. Aggrieved. Ecstatic. Abrasive. Certain. Doubting. Chastened. Paranoid. Awed. Peeved. Thankful. Since the superstar of the Psalter, Psalm 23 ("The Lord is my Shepherd"), is calm and peaceful, people tend to think they are all green pastures and still waters. Yet the majority are requests, surrounded by praise poems, creation poems, war poems, justice poems, royal poems, cursing poems, penitential poems, temple poems, Torah poems, and miscellaneous others. Oddly, the effect is not disorienting. Between topics and tone, they create a character as singular and pungent as any in literature or history—think Ahab crossed with Rumi.

They are almost painfully intimate. The "You" in the most powerful psalms is not the "you" of the throne room or even the office. It is Martin Buber's "Thou," our ultimate confidant—some of these things you would not share with your brother—the more remarkable for being the king of the universe. The request psalms are ur-kvetches: an illumination of Psalm 44 in a ninth-century Christian psalter nicely captures both the complaint's social awkwardness and its imperative. Three worried angels on either side of a big, canopied bed transmit the psalmist's uninhibited demand, "Wake up, O Lord! Why do you sleep? Get up!"

There's that voice. Aggressive. Aggrieved. Ecstatic. Abrasive. Certain. Doubting. Chastened. Paranoid. Awed. Peeved. Thankful.

My favorite psalm is 139, a study in a specific sort of intimacy, the kind where your loved one is a tiny bit too close—a naturally occurring dilemma if He is omnipresent and omniscient. "You know when I sit down and when I rise up; you discern my thoughts from far away," explains the psalmist. And somewhat irritably, "Where can I go from your spirit? Or where can I flee from your presence?" Eventually he succumbs to God's loving full-court press: "Search me, O God, and know my heart; test me and know my thoughts, and lead me in the way everlasting."

The thing is, if you remove Psalm 139's periodic use of "O Lord," and replace it with "My Love," or even with "Mom," it will still make sense. So recognizably has the psalmist nailed a certain kind of relationship that the psalm can apply to anyone with whom one is truly, madly, deeply sharing one's life. More abstractly, it can refer to any overpowering truth or state of mind whose presence seems essential, but demanding.

It is this kind of abstraction that the Zen Buddhist monk and poet Norman Fischer employs in a book called Opening to You: Zen-Inspired Translations of the Psalms, an object lesson in how the Psalter can speak to people of other traditions or no tradition.

Fischer, who grew up Jewish, regards the Psalms as a "necessary" complement to American Buddhism. But since Zen doesn't recognize a deity, Fischer had to deduce a Buddhist cognate for the Psalms' God. Noting that one of His most important roles is as the sovereign who confers sovereignty to His people, he suggested that the Buddhist version could be the high consciousness attained by some practitioners via mindfulness. Thus the Psalms become a variety of mindfulness. For the words "Lord" or "God," Fischer often substitutes "you," which for him emblemizes the act of recognizing something beyond ourselves; indeed, "all that immensity that surrounds us, inside and outside of us."

Fischer's translations are beautiful. They suggest that his Buddhism has a deep emotional capacity. And conversely, that the Psalms are big enough to encompass forms of spirituality that initially seem foreign to them.

Fischer's version of Psalm 46 reads, "You are our protection and our strength... When the sea's waters roar and foam, and the mountains quake and tremble... we know you are with us / Our defense at the silent center of things.“

Or, as Ira Gershwin would put it, "Our love is here to stay."

David Van Biema, formerly the chief religion writer for Time magazine, is writing Speaking to God: A Cultural History of the Psalms for Simon & Schuster. He lives with his wife and son in Manhattan.