Kuk Harrell, Justin Biebers Vocal Producer

LOS ANGELES Two days before Justin Biebers 18th birthday he was, as usual, working. He walked into the main control room at Record Plant, a recording studio here, his blue-and-pink high-top Balenciaga sneakers unlaced, nodding his head to a sinuous beat blaring over the speakers.

Chad Batka for The New York Times

Kuk Harrell, a vocal producer, has a client roster that includes Justin Bieber, Jennifer Lopez and Rihanna.

On this Tuesday night in February Mr. Bieber was a few weeks into the recording process for his second full-length album, Believe (RBMG/Island). The studio was crowded with songwriters trying to turn that beat into a hit; with Mr. Biebers relatives, in town for his birthday; with a security guard; with various assistants.

Then there was Kuk Harrell, the only person not openly vying for Mr. Biebers attention, who moved through the scrum quietly, every so often checking settings on a computer.

Mr. Harrell is Mr. Biebers vocal producer, a many-layered and amorphous job: part vocal coach, part cheerleader, part sound engineer, part therapist. At this studio hes a star too: the nameplate on a kick scooter at the front desk just says, KUK.

Pop musics universe of celebrities has widened in recent years to include producers and songwriters; theyre as crucial to what you hear on the radio as the stars, and increasingly known to the public. But there are deeper levels! of high ly specialized talent, just as integral, that often goes unrecognized.

Mr. Harrell, 47, is one of those figures, shaping the sound of radio from the shadows. His client roster also includes Jennifer Lopez and Rihanna, and his job is to make sure that the stars vocal is as powerful and flawless as it can be.

That happens in parts. In the studio, rarely, if ever, does a star sing a song the whole way through. Instead Mr. Harrell builds a gleaming whole from granular bits. A singer working with Mr. Harrell covers a few bars a line or two, maybe four over and over, with different emphases and inflections, until Mr. Harrell hears what he wants. The process repeats for each section. Only later, after the singer is gone, does Mr. Harrell stitch the best pieces together, Frankenstein-like, into the song you hear.

On this February night Mr. Bieber retired to a smaller studio in the back of the building to work on Sunday Morning, an aching midtempo ballad, warming up by singing long stretches of the song. But once Mr. Harrell sat down at the computer, they broke Sunday Morning down into small vocal bites, with Mr. Bieber sometimes echoing what Mr. Harrell sang to him moments before. All the while Mr. Harrells eyes remained fixed on the computer screen, where each new take was represented in ProTools, the production software, by a jagged line, like heart-rate tracings on an EKG, inside a brightly colored rectangle. The data were piling up.

Stitching the Best Bits

Vocal production can be a tedious task, requiring patience, indulgence and discipline. Mr. Harrells work begins long before his client shows up, as he determines what kinds of microphone, preamplifiers and compressor will be best. When the singer is ready, he kicks into high gear, nudging so that each line, each syllable, is sung a few different ways.

Ill take it in ! chunks, Mr. Harrell explained, sitting in his all-white apartment the day before the Bieber recording session. If they sang it amazing, Ill get the first chunk and go, Oh that was beautiful. Boom. Ill drag that up.

The process then repeats. So Ill begin to search through all the playlists I have of that moment and go, Ah, there it is, then Ill drag that moment up into the comp the compiled vocal and so on. All the way down, until I get to the end of the record and have a complete final comp.

In the studio hes enthusiastic but calm, direct and not sycophantic. Lean and slight, hes got a high hairline and long curtain of hair that recalls the comedian Katt Williams. Most of the time hes at the computer, a cap often pulled low over his eyes, his back upright and rigid. Even though hes seated, he appears to be on tippy toes.