The numbers show the problem:

In the 1987-88 season, 83 percent of the Philadelphia Orchestra's listeners were subscribers.

Last season the number dropped to 62 percent.

Single-ticket sales have increased at the same time, somewhat. But the reason this trend spells trouble is that having buyers who commit to six, nine or 12 concerts at a time is extremely cost-efficient.

To sell $300 in seats to a single-ticket buyer, the orchestra spends about $75 in marketing, advertising, postage, printing and other expenses.

Netting a new subscriber who spends $300 for tickets costs the orchestra $90.

But getting a current subscriber to renew shows why the orchestra clings to the subscriber model. Renewals are

really

cheap, costing the orchestra about $18 to $27.

The orchestra has made a number of changes in the last decade to combat subscriber-drain - more flexible exchange policies and allowing listeners to assemble their own concert packages.

But this fall it will unveil its most radical change yet: a membership program that combines PhillyCarShare's last-minute flexibility with amazon.com's marketing acumen and maybe some of Starbucks' get-it-anyway-you-want-it solicitousness.

The new program is called eZseat. Once you're a member, you can buy a ticket at a 25 percent discount at almost any time - from an hour before a concert to nine months before curtain.

Different membership levels carry different benefits. A $50 annual membership allows access to orchestra-level seats in Verizon Hall; $75 for both first-tier box and orchestra-level seats.

The program, whose research and development was funded by the Pew Charitable Trusts and Neubauer Family Foundation, will exist solely online. Members can print out their tickets, whose bar codes will be scanned at concerts by ushers. Membership grants the ability to buy tickets for regular subscription concerts, not family concerts, chamber music, or special events such as the Academy of Music anniversary concert.

The eZseat program was crafted in large part by orchestra marketing chief J. Edward Cambron as a response to increasing resistance to the old subscription model.

"We were looking for how to find a new way to get people to go regularly, as if they were subscribers, but not have the problems subscriptions have, because subscriptions are not the future," Cambron said.

While subscription erosion is not unique to the orchestra, it has hit the group hard, since there was a time a couple of decades ago when, reputedly, demand was so high the only way a subscription could be had (at least for certain seats) was by inheriting it.

In the last few years, though, even with the lure of a new concert hall - a hall with 500 fewer seats than the old Academy of Music - the orchestra has had a harder time selling tickets.

"If you go back to the heyday of subscriptions, which was the '60s, in a lot of families only one spouse worked. There was a lot more flexible time," Cambron said. "Today, for almost everyone, both heads of household work, so time is more valuable. There are also a lot more options, a lot more things in the house that provide entertainment. I think people can't plan that far ahead."

(Overall, the percentage of the hall that is filled for orchestra concerts has dropped since the orchestra moved into its new home in the Kimmel Center, from 99.9 percent in 2001-02 to 84.6 percent in the season that ended last month.)

Cambron also cites the trend of buyers' increasingly getting exactly the thing they want, when they want it.

EZseat, he says, provides the "ownership" factor of subscriptions, the benefits, but more flexibility.

"They want to go when they want to go, and you risk people not going because they either don't feel like they belong or can't get the kind of access to concerts they want. This program gives them a guarantee in a way."

The "guarantee" is that the orchestra will set aside specific seat inventory for eZseat members, perhaps 15 to 20 for each concert. If a concert looks as if it will sell out, the orchestra will send out an e-mail to members advising them to buy seats immediately.

Cambron hopes 1,500 members will sign up in the first year. Members will be counted as subscribers - of which there were 23,385 this last season - regardless of how many concerts they actually attend.

The orchestra is also unveiling a student corollary to eZseat, called eZseatU. For a $25 membership fee, students can attend an unlimited number of concerts free.

That will augment the Student Understudy program, which allows students to fill unused seats for $8 to $10. Last season, about 3,500 spots were sold to students, about 41 per concert.

This year, on Sept. 25, students will be greeted with a free Philadelphia Orchestra concert of Tchaikovsky, Haydn and Lutoslawski just for them - and then an after-party.

The orchestra performing a free concert is an extraordinary event. Why do it?

"Engaging students who are, a lot of them, new to Philadelphia right when they get here as freshmen is a great way to get music to be an ongoing part of their lives," Cambron said.

Contact culture writer Peter Dobrin at 215-854-5611 or pdobrin@phillynews.com. Read his blog at http://go.philly.com/artswatch.

Find out more about eZseat at: http://www.philorch.org/styles/poa02e/www/ezseat.html or call 215-893-1999.