AS symbolic shifts go, two recent events in pop music couldn’t have been more illuminating. On Nov. 24 “Burlesque,” a big-screen musical starring Christina Aguilera, opened and landed with a thud, both critically and at the box office. On Dec. 2 came the Grammy Award nominations. Among releases up for the album of the year award are those by Lady Gaga and Katy Perry; Ms. Aguilera, who also released an album, “Bionic,” in 2010, was ignored.  Such turnover is part of pop’s constant process of renewal: out with the old idols, in with the new. But the ground shifted under pop in an even bigger way. As seen and especially heard in “Burlesque,” Ms. Aguilera has been one of the foremost practitioners of the overpowering, Category 5 vocal style known as melisma. The female pop stars who have dominated the charts this year rarely opt for that approach. Their ascent makes it clear that melisma has retreated, while pop, which has just wrapped up one of its best years in at least a decade, has benefited from a return to less frilly, less bombastic vocal showcases.  Although there’s nothing simple about it, melisma in its simplest form is a vocal technique in which a series of notes is stretched into one syllable. Its roots can be tracked back to gospel, blues and even Gregorian chant; Ray Charles, Aretha Franklin and Stevie Wonder used it sparingly early in their careers.  But beginning two decades ago, melisma overtook pop in a way it hadn’t before. Mariah Carey’s debut hit from 1990, “Vision of Love,” followed two years later by Whitney Houston’s version of “I Will Always Love You,” set the bar insanely high for notes stretched louder, longer and knottier than most pop fans had ever heard. A subsequent generation of singers, including Ms. Aguilera, Jennifer Hudson and Beyoncé, built their careers around melisma. (Men like Brian McKnight and Tyrese also indulged in it, but women tended to dominate the form.)  That melisma heyday is jarringly invoked on Ms. Carey’s current album, “Merry Christmas II You,” a collection of seasonal standards and originals. One of the tracks, a rendition of “O Holy Night” recorded in 2000, is a reminder of the days when Ms. Carey and her voice were in full melismatic overdrive.  Whether it’s because of public fatigue or the advancing ages of its mainstays, who can’t quite sandblast the high notes as they once did, those days appear to be over. Ms. Aguilera’s “Bionic,” along with recent releases by Ms. Carey (“Memoirs of an Imperfect Angel”) and Ms. Houston (“I Look to You”), have sold far below their usual multimillion levels. “American Idol,” whose contestants have long been clearly influenced by melisma, is in ratings and buzz decline.  Beyoncé and Pink, who embraced melisma early in their careers, have both left it behind. Pink’s new compilation, “Greatest Hits ... So Far!!!,” is dominated by her rock-leaning rasp, whether she’s taking a crack at a ballad (“Dear Mr. President”) or a party anthem (her current single, “Raise Your Glass”). Although she was fond of elongated syllables while a member of Destiny’s Child, Beyoncé gradually moved away from brassy displays. Her luminous recent hit “Halo” has only a suggestion of melisma. It’s telling that her most recent hit, the irresistible dance pop song “Telephone,” is a collaboration with Lady Gaga.  Starting with Lady Gaga and Ms. Perry the nonmelisma female performers who have taken over iPods and the radio couldn’t be more different vocally. On “California Gurls” and “Teenage Dream,” her ubiquitous 2010 hits, Ms. Perry opts for short, breathy gulps in her singing. Her voice occasionally glides into an upper register, as on the bridge of “California Gurls,” but it mostly aims to convey likability and approachability, not prowess and imperiousness.  As heard on her current single “We R Who We R” from her new mini-album, “Cannibal,” Kesha has a thin, often computer-manipulated voice that recalls ’80s new-wave pop acts. It’s often hard to tell when her singing voice ends and the Vocoder processing kicks in.  The technically best singer of the bunch, Lady Gaga, has a deep, mildly nasal delivery that, on hits like “Alejandro,” evokes a more tuneful Madonna. Her version of melisma is more visual than aural: her Broadway-inspired stage shows, arresting videos, Warhol-redux costumes and exploding bras are over the top, as opposed to her singing.  What all those singers have in common is a delivery far less virtuosic than the melisma queens of old. (Some, like Taylor Swift, they may not be vocally capable of it either.) None is likely to inspire contestants who will stand before Jennifer Lopez and Steven Tyler on the next season of “American Idol.” Rather than wrestling the melodies to the ground, these singers adhere closely to them. The high notes Ms. Perry reaches for on “Teenage Dream” are the merest of vocal trills. One of the year’s most arresting hooks, Rihanna’s contribution to Eminem’s “Love the Way You Lie,” conveys sadness and regret in a beautifully understated manner devoid of vibrato.  What makes singles like “Telephone” and “Alejandro,” “California Gurls” and Kesha’s “Tik Tok” and “Your Love Is My Drug” stand out aren’t the voices at their core. It’s the combination of vocal personality, arrangement, hook and songcraft — the eternal, enduring ingredients of classic pop. Even their voices are turned into hooks: one of the most memorable parts of “Telephone” is the moment Lady Gaga’s voice imitates a busy signal.  Those songs were also central to this year’s invigorating resurgence of pop. From the teen-bop star Justin Bieber to the casts of “Glee” and the boy-band TV series “Big Time Rush,” dance-infused pop singles made a triumphant comeback in 2010. Beats and melodies once again became the stars — a welcome reprieve from the melisma era, when emphasis shifted from songwriting to Olympic-style displays of lung power. To test the damaging influence of melisma, one need only try to hum one of Ms. Carey’s vaporous hits all the way through; it’s virtually impossible.  Melisma may have also run its cultural course. Ms. Carey, Ms. Houston and Ms. Aguilera, to name its three main champions, are most associated with the period from the late ’80s through the late ’90s: an era now largely associated with money, ostentation and American power, especially during the latter half of the ’90s. Their brawny vocal approach and lush, widescreen records reflected their times as much as the Clinton-era Wall Street boom.  Pop’s new divas may not be able to ascend to vocal heights the way Ms. Aguilera still can in “Burlesque.” But in many ways they’re better suited for the post-crash economy. Every so often even pop music has to downsize.
Melisma â the vocal technique of packing notes into one syllable â was long championed by singers like Mariah Carey. New stars like Kesha eschew such pyrotechnics.