Veteran country-pop hitmakers Diamond Rio make an easy transition into Christian music with The Reason, an album that should please old fans while winning new ones. Marty Roe’s warm, lightly twanging lead vocals blend with his bandmates’ harmonies as smoothly as ever. What’s different here is an explicit focus on God and the role faith plays in everyday life. Many of these songs draw upon personal experiences to express spiritual truths — the title track contrasts the emptiness of showbiz fame with the blessings of redemption, while “What Are We Gonna Do Now” offers a heartfelt eulogy for bassist Dana Williams’ pastor. Tunes like “God Is There,” “Just Love” and “This Is My Life” find the presence of the Lord amidst ordinary struggles. From the soulful acoustic feel of “My God Does” to the rousing big-harmony sound of “In God We Still Trust,” the band explores the full range of their capabilities. Especially resonant is “Moments of Heaven on Earth,” a look at the ups and downs of marriage from a Christian perspective.