Musiq Soulchild sometimes let his voice get away from him at the Birchmere. (All photos by Marlon Correa/TWP)The most relatable, youthful and mainstream of the artists who popularized “neo soul” more than a decade ago, Musiq Soulchild exudes sincerity and simplicity.

At his show at the Birchmere on Sunday night, he relied on first-person narratives that touch the listener in that “me, too” place. Musiq tapped that strand of empathy on “Be Friends” from this year’s “Musiqinthemagiq” album, getting a rise from an ad hoc amen corner remembering difficulties with post-relationship friendships. A snappily delivered song about turning away from temptation when you’re no longer on the market, “Single” benefited from the same effect.

Musiq’s strengths are great melodies and big, happy choruses, often so sweet they feel like guilty pleasures for those who prefer more serious soul music with fewer concessions to contemporary R&B. “Love,” “Girl Next Door” and “B.U.D.D.Y.” were highlights from his back catalogue, combining irresistible arrangements with confident ex­ecu­tion.

But behind all of the smart pacing, high energy, solid musicianship and witty engagement lurked a few unfortunate vocal failings. Although he’s far from a rookie, Musiq’s abuse of melisma occasionally sounded like that of an early-stage “American Idol” contestant. Unnecessary runs careened off course and stopped on odd sharp notes that didn’t resolve. Sometimes those runs would just bottom out inaudibly at the end of a phrase, as if he got lost and gave up.

Musiq sings in a head voice that is pleasant in the middle of its range but wasn’t nimble enough to handle frequent jumps in and out of the falsetto that he relies on for some of his most beloved songs. Simultaneously lustful and affirming, “Sobeautiful” is a lush piece of R&B balladry whose demands exceeded Musiq’s vocal abilities.

During a heartfelt spoken interlude about the difficulties of soul artists making it in the biz today, Musiq expressed thanks for having succeeded this long and said he’ll be blessed if he can still be singing these songs when he’s 60. He definitely has a much better chance at that longevity than today’s R&B stars, but hopefully he’ll continue to develop his instrument.