The newest block to fill up downtown hugs the backside of City Hall. Along West Second and Guadalupe streets, the project looks like nothing more impressive than a near-windowless black box four stories tall.

Loading docks and delivery entrances meet the eye on West Third Street. Only along Lavaca Street does the block reveal much. A three-foot white W and a covered driveway crescent signify the entrance to the oh-so-hip W Hotel, which opened Thanksgiving week. Thirty-seven floors of hotel rooms and condos tower above.

Unmarked stairs just finished at the corner of Lavaca and West Second streets lead into the black box part of this hybrid building, which is where thousands of Austin music fans will be headed this week. With a mouthful of a name, ACL Live at The Moody Theater opens its doors Thursday evening.

Not since 1981, when the University of Texas debuted its Bass Concert Hall, has Austin seen an all-new indoor performance facility of this size. With a capacity of 2,750, just under Bass, ACL Live will specialize in popular music acts and double as a television studio for the "Austin City Limits" show.

The $300 million development project by Stratus Properties has been five years in construction. More than $40 million of that cost is wrapped up in the ACL Live side of the block, where, for the past few weeks, crews have worked 24 hours a day installing seats, bars, lighting, stages and sound equipment. A few flourishes will come after the opening, such as minimal exterior signage and a larger-than-life bronze Willie Nelson statue at the foot of the entrance stairs (Capital Area Statues Inc. is still raising money for completion and expects a summer installation).

The first few months' bookings for ACL Live portend a something-for-everyone buffet. The opening concert on Thursday is a family event by Disney's Imagination Movers. Then come two $5 concerts (Cody Canada and the Departed, Los Amigos Invisibles with Trombone Shorty), two nights of Willie Nelson, the Swedish pop of Robyn, a gala benefiting KLRU public TV with Steve Miller, the arena rock of Styx and the softer sounds of Diana Ross.

If ACL Live delivers the 60 to 100 concerts a year that it promises, the hall could overshadow the less frequent popular music offerings of Bass Concert Hall, the Erwin Center and the Long Center for the Performing Arts. Those large venues will continue to fill seats mostly for theater, classical music and other performing arts, comedy, sports, circuses, and giant production acts such as Lady Gaga at the Erwin in April.

With its Austin City Limits moniker, the new player in town is likely to confuse some people. The ACL Live concerts will not be taped for television's longest-running music series. "Austin City Limits" will schedule its own separate shows (KLRU has use of the hall 45 days a year), and sometimes the same act will do both a concert and a taped show on different days. The concert tickets are sold. Tickets for tapings are free for the increased audience of 800, but getting on the guest list requires connections to sponsors, staff or acts, or winning drawings on the austincitylimits.org blog. Got that?

"It was a little confusing in the beginning, but (talent) agents got the word and now understand. The buzz is out on us," said Colleen Fischer, who is booking ACL Live. "The public will learn the differences."

She readily acknowledges that "the historic role of 'Austin City Limits' is what's going to give this building its soul."

Terry Lickona, executive director of the TV series, will have an office in the building along with Fischer, who previously booked the Houston music venues of Rockefeller Hall and Verizon Wireless Theater. She said she and Lickona have shared their booking wish lists for a wide variety of acts. "It's important that this room has a big diversity and I'm not limiting my audience," she said.

The partnership will be obvious to anyone strolling the wide hallway gallery outside the mezzanine-level seating. For more than 100 feet, photos and artifacts from the past 36 seasons of "Austin City Limits" will be displayed, much of it collected for exhibit at the Rock and Roll Hall of Fame and Museum in Cleveland. Plans are afoot for daytime tours of this area and the studio space.

Jeff Peterson, a longtime producer of the show, has worn a project manager's hard hat in the building nearly full-time for the past two years. He said the overarching goal he and Lickona insisted upon was to be able "to record in a pristine manner." Sounds simple, but Peterson said they couldn't just copy another dual-use facility. "We didn't find a single other place that combined a state-of-the-art audio and recording capability with a midlevel performance venue," he said. "Everything in this building started with our studio template."

So the main floor was built with two concrete slabs and an acoustic mat in between. A track for a remote-controlled camera is slung beneath the mezzanine level to get views to supplement the six or seven manually operated floor cameras. The director's control room behind the stage features walls seven layers thick on each side of the door and a ceiling hung on sound-isolating mounts. Fans will have to push through two sets of heavy soundproof doors to get to their seats inside the hall.

The stage for the television productions is topped with distressed wood painted the same dull brown color as the old stage in Studio 6A at KLRU and just seven feet wider. A bigger, higher and more malleable stage will be used for live concerts. Early plans to dismantle the historic TV stage and rebuild it downtown were scrapped because of structural integrity issues.

To continue the look of the show, a green tree limb or two will be hung over the audience's portable seat risers. The stage backdrop of the Austin city skyline at night has been re-created and updated to add new buildings, size and durability, which required a team of six designers at a cost of roughly $200,000. "ACL" is keeping the mural behind curtains for an unveiling Feb. 24 at the KLRU fundraiser.

For the ACL Live concerts, a dozen bars on the floor, mezzanine and balcony levels should keep audiences sated. For the taped shows, fewer bars will be open and no free beer will be handed out, one of the famous perks for the old TV audiences. State liquor laws covering the new commercial facility nixed that.

A feature touted by all is how close the front of either stage will be to the farthest seat in the house: 75 feet. Despite its capacity of 2,750, the high-ceilinged, wraparound room appears almost cozy compared with some other local concert halls. For most tapings, the balcony will be curtained off and floor riser seats moved in to create a club-like feel.

Attending a sold-out concert will challenge downtown parking skills. The garage under the building is for W Hotel guests and condo residents. Concert-goers will be on their own to find streetside spaces and parking garages. Fortunately, the City Hall garage, AMLI apartment garages and a state garage are all within easy walking distance and mapped on the ACL Live website.

Every detail of the new building might not be finished by Thursday evening when four guys in bright blue jumpsuits get down to their happy business as Imagination Movers. But the essentials are in place: seemingly endless wiring for lights, sound and the networks of computerized equipment; 14 restrooms; and hundreds of seats — all black leatherette, all with armrests and drink holders.

The army of hard hats who've occupied the big box finally will be replaced by music fans. And the new ACL Live staff and the old "Austin City Limits" staff will get on with their marriage.

A view from the stage

The performers' view from the original home of ‘Austin City Limits' in Studio 6A, left, and at the new ACL Live venue downtown. 'ACL' producers plan to maintain an intimate feeling by keeping capacity to around 800 for most tapings. At the new venue, the farthest seat from the stage will be only 75 feet away.

Austin City Limits Live at The Moody Theater

310 W. Second St.

225-7999, www.acl-live.com