LOS ANGELES—To all the performers who justify lip-syncing because they are so breathless from dancing, we have one name for you: Justin Timberlake.

For nearly 3 hours last night at the re-opened Forum here, he proved he is a true song-and-dance man, as the agile entertainer was a perpetual man in motion for the entire show.  While ably assisted by four strong back-up singers who did some of the heavy lifting during certain songs and some judiciously placed backing vocals, for the most part, Timberlake sang live throughout the evening. What a concept…

Dressed in a white tux, he spanned his entire post- ’N Sync career, but focused, as one would imagine, the bulk of the show on songs from both volumes of  “The 20/20 Experience,” last year’s top selling release.

The issue with many of the songs on the two albums—the lack of identifiable hooky choruses —was amplified in concert as many of the songs indistinguishably segued from one into one another. Timberlake clearly designed a show to shift effortlessly between songs, but the absence of clearly defined melodies in some cases just meant masses of music that were no different from the song coming before it or after, unified by a repetitive throbbing beat.

Timberlake was also plagued by atrocious sound, especially for the first half of the concert. The Forum reopened last week after a $100 million renovation. The Eagles, who are playing six shows here as part of the rebranding, showed that for clear voices, harmonies, and acoustic instrumentation (with some electric guitar and bass thrown in), the acoustics are great. But the sound system was not prepared for what Timberlake’s band of 15, JT and the Tennessee Kids, threw at it and the bass-heavy beats echoed off the low ceiling throughout the evening in ways that were both earsplittingly painful and distracting. But worst of all, they often so overshadowed Timberlake’s vocals as to drown him out almost entirely.  Even on songs that were meant to be softer and toned down, such as the excellent “Drink You Away,” which he performed surrounded in a semi-circle by his band, suffered from over amplification.

When he was audible, such as on “My Love” or a pumped-up “Cry Me A River,” he sounded great, ably shifting from his normal voice to his instantly-recognizable falsetto effortlessly.

The production values were state-of-the art. A huge white honeycomb-patterned screen filled the entire back of the stage, leaving no room for the jumbotrons that usually flank the stage). Throughout the night different images were projected on the screen, including close ups and video pieces for a constant barrage. About a third of the way into the second half, Timberlake and his four backup singers rose high above the audience on a plank from the stage that transported them to the back the arena. While artists flying over the crowds in buckets or bridges is almost commonplace in big arena shows now, the lighted up plank, with stairs reaching out on the sides, was far more elaborate than usual. Timberlake  and the singers spent more than half an house on the plank dancing and singing before coming down to a stage in the back of the house where he performed a choice cover of “Heartbreak Hotel,” by fellow Memphis son Elvis Presley, and “Human Nature,” by his hero, Michael Jackson.

There’s nothing Timberlake doesn’t do well and to watch him sing full out after dancing a complicated routine time and time again was a tribute to his professionalism, talent, and hard work. And he seemingly did it all without ever breaking a sweat…and in a cummerbund.

By the time he closed the show with a gorgeous version of “Mirrors,” he still had enough gas in the tank to deliver a heart-felt energetic take on the best song from “The 20/20 Experience Vol 1.”

While all the bells and whistles may play to the back row, Timberlake is an artist who truly doesn’t need any of that, which is what makes him such an exceptional entertainer. It’s a shame that a muddy sound mix prevented him from being heard at his best.