After establishing himself in Christian music circles some years back, Matt Wertz seems poised to take a leap into the secular mainstream. Under Summer Sun features the best cuts from his last two albums along with newly-recorded tracks, and taken together these tunes present the Missouri-bred singer/songwriter as a footloose young romantic in the mold of John Mayer, Jason Mraz and (especially) Dave Barnes. As a vocalist, Wertz’s breathy delivery and softly rhythmic phrasing lend a laid-back appeal to “Marianne,” “Everything’s Right,” “5:19” and other pop-rock exercises. The tracks benefit from uncluttered production, veering from sparse folk-pop (“Back In June”) to inviting light funk (“The Way I Feel”) to balmy disco-inflected grooves (“Summer Sun”). With the exception of the uplifting “Keep Faith” and the solemn “I Will Not Take My Love Away,” the songs generally avoid explicit spiritual language. Wertz’s boyishly disarming persona shines best on “Waiting,” a quietly confessional piece set to a delicately wrought melody line. Under Summer Sun feels undemanding in some places but deserves kudos overall for its breezy musicality and warmhearted vibe.