On Thursday night more than 500 musicians, composers and others active in the Hollywood music biz heard a panel of experts warn that film, TV and videogame scoring continues to leave L.A. because producers are unwilling to meet union demands.

If work continues to dry up at the current rate, they speculated, one or more of the three remaining large scoring stages (Fox, Sony, Warner Bros.) could close “within the next two to five years,” leaving London as the new scoring capital of the world and cheaper locations like Prague and Bratislava as second and third choices.

Union officials, who were not present at the meeting, are disputing the version of facts as presented Thursday night. They say that although work is down, a larger percentage of current film work is actually staying in the U.S. They deemed it “no coincidence” that the meeting was held just as the American Federation of Musicians was negotiating with the AMPTP for a new film and TV scoring contract.

The meeting at Santa Monica High School was organized by Cinesamples, an El Segundo-based company that has run up against AFM opposition to its plans to record L.A. musicians for its music-sampling business.

The mood among musicians during the three-hour session ranged from confusion to desperation about the recent decline in demand for L.A. musicians to score major features and nearly all videogames.

Composer manager Richard Kraft (who represents Danny Elfman, Alexandre Desplat and others) said that the “automatic assumption” that a film would be scored here has recently become more like “how quaint, we’re going to be recording in L.A.”

AFM long ago negotiated contract clauses that provide for union musicians to benefit from the sale of movies to TV and other ancillary markets and also provided for additional payments if the music recorded for a film or game is later used in another context such as a soundtrack album. Game publishers generally refuse to sign any deal with the union that doesn’t allow them to own and control all the music in perpetuity without having to spend more later.

Producers and publishers avoid this in non-AFM locales (London, Prague, Bratislava, Seattle, etc.) through a “buyout” clause that enables producers or game studios to pay more to musicians upfront and then walk away without future financial obligations.

According to Kraft, the AFM demand for producers to agree to make future backend payments to musicians based on the sale of films to TV and other ancillary markets has become a “conversation stopper.” Increasingly, he says, producers simply opt for London.

The widespread perception, Kraft said, is that L.A. is no longer competitive. Only one of the five top-grossing films of the year (“The Amazing Spider-Man”) was scored here; “Brave,” “The Dark Knight Rises,” “The Avengers” and “The Hunger Games” were all scored in London.

Composer Christopher Lennertz, who is active in all three areas (currently scoring TV’s “Revolution”), reported that scoring decisions “always come down to the backend,” meaning the demand for later payments by producers. “If there was no backend, I could record anywhere,” he said.

Lennertz shared a memo from Steve Schnur, music exec at game publisher Electronic Arts (and a longtime proponent of scoring games in L.A.), that indicated he has given up on L.A. and will now score everything elsewhere. “Basically, they are driving me out,” he wrote about the AFM. “Till it changes, we’re gone.”

Composer Garry Schyman (“BioShock”) said that the latest AFM game contract, which takes effect Dec. 1, will assure that “millions of dollars’ worth of scoring work is not going to come here,” going instead to places like Nashville, where union musicians are allowed to work non-union because of Tennessee’s status as a right-to-work state.

He proposed a six-point plan to stem the tide of work leaving L.A., including more competitive rates (currently it costs about $100 per hour to score a game in London vs. about $150 in the U.S., panelists said) and a “change of attitude” on the part of AFM officials. “A serious percentage (of the work) could come back to L.A.,” he said, if musicians become more active and convince union leaders to shift positions.

According to Film Musicians Secondary Markets Fund administrator Dennis Dreith, “Yes, there is less work. That’s not in dispute.” But, he points out, fewer films are being made (about 150 wide releases per year, down from 375 a few years ago), and according to Dreith, a larger percentage of those films is actually staying in the U.S. to score.

He notes that the fund — which receives that backend money from the studios — just had its second biggest year ever, collecting $84 million for musicians, and is on track for another record year, having already collected $44 million in the first half of this year.

He also points out that working musicians have, since 1960, benefited from the fund. “Every other guild and union in the industry has a backend payment structure exactly like ours, except at a much higher percentage,” Dreith says. “We get the lowest percentage of any guild.”

Reached on Friday, AFM president Ray Hair said that “work has always left town. I’m not going to answer these questions by gutting our agreements with employers. I understand that folks wish the rates weren’t so high. But the mistake people make is thinking that if you do away with (rights) that we have bargained, all of a sudden they’ll have what they want. Show me a situation where that’s ever happened.”