HOUSTON — The children’s choir spaces around the microphone at center court and the Washington Wizards and Houston Rockets players stand at attention. During this a cappella rendition of The Star-Spangled Banner, some players sway in place, others stare at the flag that hangs from the rafters and John Wall closes his eyes, waiting on his cue.

It’s a scene that happens before every NBA game. Whether he hears the notes from a seasoned singer or the adolescent voices of a school chorale, when the national anthem reaches its conclusion — o’er the land of the free — Wall rolls up the right sleeve of his warm-up jacket, caresses his plastic wristband, kisses both wrists, points to the sky and turns to his left to find Bradley Beal. Then, the Washington backcourt performs their greeting, a special ritual invented over the summer.

“We always had a handshake but it would be a basic two times,” said Wall, describing the consecutive open-palm slaps done in quick succession that he shares with every teammate. “Then we were like, ‘That’s boring … we should add something to it.’ ”

The Wizards (42-36) have endured an inconsistent season, but their pregame routines — spiritedly performed with grace and enthusiasm each and every game night — have remained steady.

After Wall and Beal’s handshake — one open-palm followed by two backhanded slaps and a series of finger gestures concluded by locking indexes — then a swirl of choreographed chaos begins.

Markieff Morris and Tim Frazier inch closer together by dribbling between their legs before throwing down an imaginary reverse dunk.

Kelly Oubre Jr., the one responsible for the most elaborate greetings, waits for this routine to complete, his hand on his hip. Then when Frazier comes over, the pair slaps hands forward, then backward and nod their heads in extravagant fashion.

Beal includes the Wizards’ staffers. He takes the stance of a center at the line of scrimmage and hikes his warm-ups to the team’s assistant athletic trainer, Jeff Bangs, who’s squatting a few feet away like a quarterback. Then, just before taking the court, Beal walks the sideline, shakes the hand of assistant David Adkins and strokes his necktie.

Mike Scott slaps the back of Jodie Meeks’s neck, Meeks returns the favor then the duo shuffles their feet side to side.

Ian Mahinmi stiffens his upper body and goes around shrieking and shoulder-checking everyone in sight, as teammates pretend to be bowled over. (“We do his because every time he gets fouled or touched or anything, he always does this thing,” explained Jason Smith, who then mimicked Mahinmi’s howl of pain. “So that’s why he’s walking through, trying to be a strong man.”)

Also, ‘Shorty’ and ‘Five,’ the nicknames that Morris and Wall call each other, respectfully, execute their personalized handshake. Much like the reason Wall calls his 6-foot-10 teammate ‘Shorty’ — “I don’t know. Just something I came up with. A lot of people call him Keef. I just call him Shorty,” Wall said — there is no rationale to the routine that Morris describes as, “Two on one.”

The handshakes make no sense. They’re just fun.

“It keeps you in good spirits,” Beal said. “Gets everybody ready to go.”

Smith, the energy guy, has a move that reflects his personality. Before the game and even after huddle breaks in timeouts, Smith gets his low-fives with a little extra bounce. Beal was the first to hop and skip while greeting Smith, who just rolled with it. Otto Porter Jr. noticed.

Smith recalled Porter asking one day why he does that. “I’m like, ‘I don’t know. Brad does it.’ ”

Then, Porter started hopping with Smith, too.

When Smith interacts with Frazier, however, he gets a simple, firm handshake because Frazier “says I’m a professional.” Smith’s also a father of two young children, which may explain why his handshakes are a bit more subdued than, say, the series of slaps and swipes and sways staged by his teammates.

“It takes a lot to remember those handshakes,” Smith said. “You really have to get off the court and practice it in the locker room. Eh. I got kids.”

According to Rockets center Clint Capela, the secret to a perfect pregame routine is simply repetition. Capela has shared an involved handshake with James Harden for two years. Although the end has changed — the players have mixed in various dab dance moves — the beginning  was created during the 2016 training camp and has remained consistent.

“The thing is just to repeat it. Before practice, we’re going to do it. During practice, like, between drills, we’re going to do it. After practice, we’re going to do it. This is where it gets to your head,” Capela said. “You both have to like it and then start practicing.”

Smith will leave that extra work to the single guys. As Smith explained the Wizards’ pregame routines, he spotted Scott coming from the across the court.

“Mike, how many different handshakes you got?” Smith asked.

“Like, eight,” Scott said slowly, trying to remember. “I’ve got one for everybody.”

Admittedly, Scott does not have one for Ramon Sessions, who signed with the team in March. Personalizing each one is difficult and Scott declared he’s no pro in conjuring up new handshakes.

“You’re not good with coming up with handshakes? And yet you have, like, a handshake for every guy,” Smith said in disbelief.

Tomas Satoransky can debunk Scott’s lack of creativity claim. It was Scott who imagined their pregame greeting — the two look around the sideline confused, they can’t find one another but suddenly make eye contact and come together like long-lost friends. Also, when Satoransky stepped into the starting rotation while Wall missed 27 games, his role changed and not just on the court. Just ahead of tip-off, Satoransky would hold his hands to his head and do the ‘Hotline Bling’ dance along with team security guard David Best.

“He came up with that, all right,” Satoransky said, almost defending himself against the goofy bit. “Everything I’m doing, I didn’t come up with it. I’m just doing it since everyone’s doing it, to be part of that. And I was a starter, and the starters usually have more handshakes.”

Silly as they might be, teammate handshakes can hold a significant meaning.

“I feel like if you have a relationship with somebody … that’s more camaraderie,” Morris said. “You walk around with handshakes with everybody, that’s like a family type atmosphere.”

Wall wants to have a handshake with every person in Wizards team colors. He hasn’t yet got Coach Scott Brooks on board: “Brooks don’t get it, man,” Wall said with a sigh. “Brooks — he’s so old school. I try to get him to wear a pocket square and he won’t do it.” Also, Wall said he needs to be inspired before coming up with one for his backup, Satoransky.

“You’ve got to think about it and you don’t want to make no corny-ass handshakes,” Wall said. “I haven’t really thought about it yet but I’m trying to get one with everybody.”

At times on the court, the Wizards may seem disjointed and out of sorts. But for those minutes before the game, the handshakes show their unity.

“It’s not even just with basketball,” Smith said. “You see teachers doing it with their students when they walk in the class. It’s just something to get everybody on the same level, have some fun, make it a lighthearted environment. And at the same point for us, it kind of takes that pressure off. You want to be focused in the game but you also want to have fun in it.”

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