Local musicians who perform at Jewish weddings have a surefire way of knowing if their gig is a hit: They look for lots of empty seats.

The party is a success, they say, when the guests who occupied those chairs are out shimmying on the dance floor.

"Music makes the party," says bandleader Joel Nelson, whose group plays at 35 to 40 Jewish weddings a year. "For Jewish weddings, it seems to be one of the more important things. The spirit, the ruach, they want in the party is maybe a little higher."

Good timing and the right blend of melodies — both Jewish and secular — are key to avoiding a reception where guests are glued to their seats.

"I'm finding almost all Jewish couples we talk to say, 'Yeah, we want to get the party off right off the bat,'" says Nelson, a San Jose-based keyboard player, singer and conductor.

The Joel Nelson Band almost always kicks off with the hora and the traditional hoisting of the bride and groom in chairs. The band continues with a medley of tunes suitable for hora dancing that sometimes can last for 45 minutes, depending on the guests' stamina and enthusiasm.

For Achi Ben Shalom, leader of the El Cerrito-based Adama, a reception party frequently starts even before the arrival of the new couple, which has been spending time alone in the post-ceremony ritual, called yichud. "We gradually bring up the energy before the bride and groom come," he says, and when they do arrive, "we give them the grand entrance." The group then envelopes the newlyweds in a hora circle and lifts them up on chairs.

Michael Gill, of the East Bay-based Shtetlblasters as well as Adama, says many couples consider the band the most important component in a successful reception. A couple might want to cut back on food, he said, but is "not going to skimp on the music. I think people realize that bands can make all the difference in what they're looking for."

Adama plays a medley of wedding songs, often starting with the traditional "Od Yishama."

"Every party has its own rhythm and its own timing," says Ben Shalom, a singer and guitarist who has performed in the Bay Area for about 15 years.

Bandleaders say bridal couples are encouraged to make song selections, but just how much input they supply depends on their musical interests and background.

Werner Berg of the Limonim Klezmer Band in Santa Rosa says couples today seem more musically knowledgeable than in years past. "It used to be a matter of price and how big and how loud, but there are people out there who are musically very sophisticated," says Berg. "They want to know a lot. It's their wedding, and it's really important to them."

Many couples have developed eclectic tastes, and as a result, the musical sound they seek is more exotic than a replay, say, of old reliable selections from "Fiddler on the Roof." More and more bridal couples are asking for Ladino music and its soulful tones, according to Berg. "It's like the world knows about Ladino pieces."

At the same time, most bands, including Berg's, still get requests for the sentimental favorite "Sunrise, Sunset."

Berg jokingly referred to "Hava Negillah" as a Jewish version of the well-worn "On Top of Old Smoky." Because he's played it so often, "we bury it in a medley of the hora," he says, "so we don't have to linger too long on it."

But, it's a song that does the job: It gets guests dancing. "If that's what it takes to get them to dance, then we'll do it," he promises.

Joel Abramson, leader of the Oakland-based Joel Abramson Orchestras, has noticed lately that clients "want something more sophisticated than 'Hava Negillah.' They want newer, more Israeli music."

He's hearing more requests for Mizrachi tunes and other forms of Middle Eastern music.

Berg says the Israeli folk dance "Mayim" remains popular along with "Dodi Li" and "Erev Shel Shoshanim."

From parents of the newlyweds, Berg's group often gets requests for nostalgic tunes like "Papirosen," an old Polish piece.

For Adama's Ben Shalom, the secret to a successful gig is, "you never introduce any new song."

"You want to play songs people learned in the formative years, the kind of songs they learned in Hebrew school," he explains. "Those are the kinds of songs that bring out the joy in people; it makes them happy and brings them out dancing."

As for secular music, requests run the gamut. Lately, Nelson is hearing a few more requests for Frank Sinatra and big band music. Gill says classics like Nat King Cole's "Unforgettable" remain consistently in demand as well as Motown or Rolling Stones music. Abramson says that apart from Orthodox weddings, "you're following what's current with pop music."

Whatever the selection, bandleaders say expectations of their performance run high. It's not unusual for Abramson to field a call the week before the party from the bride or groom, telling him, "'Joel, I'm counting on you to make this the best event we've ever been to.' Does the caterer get a call like that? Probably not."