Broadway saw bustling traffic over Thanksgiving, with close to 253,000 patrons crammed into 34 playhouses. But the most crowded seating was in the orchestra pits of the St. James, the Palace, the Neil Simon and the Vivian Beaumont.Contrary to the downsizing trend that has seen Rialto orchestras shrinking over the past two decades, members of Musicians Local 802 were packed cheek-by-instrument-case in those theaters, playing revivals with original, full-scale orchestrations. The now-departed “Gypsy” — a transfer from City Center’s Encores! series — started the parade in spring 2008, with 25 musicians playing the original charts. Lincoln Center Theater’s “South Pacific” continued the trend, earning nightly ovations with 30 players. “West Side Story,” which bowed in March, retained 29 musicians, while this fall’s revivals of “Finian’s Rainbow” (another Encores! transfer) and “Ragtime” (from the Kennedy Center) are employing 24 and 28, respectively. That’s 111 union members (plus conductors) in just four theaters, compared with about 258 spread around Broadway’s other 18 musicals. But with most revivals opting for smaller-scale orchestras, and the biggest new musical of the current season, “The Addams Family,” bowing with a 17-member orchestra, it’s clear that economically, the more modest group makes sense. Downsizing still engenders some key questions, though: Does the trend toward fewer musicians have creative consequences? And can composers of new tuners expect larger orchestras for their shows in the future? The answers are a respective “yes” and “no.” Marc Shaiman, composer of “Hairspray,” points to the audible audience response when the full orchestra is revealed during the overture to “South Pacific.” “Of course the audience can tell the difference, both aurally and emotionally,” says Shaiman. “Imagine going to a spa and the masseuse offers two types of massage, one using both hands or one with just thumbs. Who wouldn’t choose the two-handed?” Contrast the full complements at the aforementioned revivals with rock-inspired combos at long-running hits like “Mamma Mia!” (11) and “Jersey Boys” (9), and you’ll see why these musically bounteous tuners are especially welcome to both audiences (who embrace the lavish sound) and musicians (who create it nightly). The traditional pit orchestra through the Golden Age of the Broadway musical and into the 1980s numbered in the mid-20s, governed by minimums negotiated between the League of New York Theaters (now the Broadway League) and Local 802. The largest houses, with 1,400 seats and up, called for between 25 and 27 players; the slightly smaller midsized theaters, like the Broadhurst and the present-day Richard Rodgers and Neil Simon, had a minimum of 20. So-called dramatic houses required 12 musicians or fewer, but only the most intimate musicals ventured into those small-capacity confines. When these houses were booked for practical or aesthetic reasons — like “She Loves Me,” at the 1,046-seat Eugene O’Neill in 1963 — a producer such as Hal Prince might well see fit nevertheless to cram in 21 pieces. The fact is, the minimums were just that: The contract was set up in such a manner that producers could, and often did, start with 30 or so musicians. The official “cut list” allowed them to reduce the orchestra to the minimum when and if business weakened. The days of the universal 25-piece band are long past; the union minimums have eroded, contract-by-contract, over the past 20 years to the point where the typical “large” orchestra is now closer to 16. Since 2004, the only new musicals to open on Broadway with more than 18 musicians have been “Irving Berlin’s White Christmas,” which, given the nature of the score and the strict supervision of the Berlin estate, might just as well be seen as a revival; Mel Brooks’ “Young Frankenstein,” helmed by a composer-producer who anticipated brisk business in his $450 “premier” seats; and “Shrek the Musical,” in which DreamWorks displayed a no-expense-spared profligacy and seemed determined to keep up with the Disneys. (In fact, all four Mouse House productions since “The Lion King” in 1997 have been in the 18-or-under range of musicians.) The largest new musical of the 2009-10 season — other than “Finian’s Rainbow,” “Ragtime” and the returning “White Christmas” — is likely to be the upcoming “The Addams Family.” Most revivals nowadays, like “Bye Bye Birdie,” “La Cage aux Folles” and “A Little Night Music,” choose to use reduced orchestrations. But does it matter? “Yes,” says Jack Viertel, who produced “Gypsy” and “Finian” at Encores! and enrolled myriad partners to move them to 44th Street. “It was understood that the music was at the heart of why people would want to buy tickets, and that this was much more important than spending money on lots of moving scenery or dazzling effects. “The full orchestra is vital to the experience the audience has. The heart of both shows is contained not just in the songs but in how they sound.” But what are the prospects for composers of new Broadway musicals, as opposed to Golden Age revivals? “Composers today are very happy to get their show on — they accept what you give them,” says 50-year veteran Seymour Red Press, the musical contractor of “Finian” and “Gypsy” (and a flute/sax player in the original “Gypsy” pit in 1959). “Richard Rodgers used to say 35, he got 35,” he continues. “Now, I don’t care who the composer is — they accept what they can get to get the show on. In most cases, the minimum is the maximum.” Shaiman, composer and co-orchestrator of Broadway-bound tuner “Catch Me if You Can,” agrees. “We have 16 or so musicians currently budgeted. Because the score is about the sound of Nelson Riddle and his contemporaries, the producers understand any less would be nonsense. “But do I wish I had 24? Oh, yes!” Steven Suskin is author of “The Sound of Broadway Music: A Book of Orchestrators & Orchestrations” (Oxford U. Press).