If you bought a ticket to the theater, or recently took an art class, or somehow participated in a cultural event, you might be hearing from the Greater Philadelphia Cultural Alliance.

For the next four weeks, for example, the alliance is coordinating an instrument drive, asking culturally engaged people — through email and social media — to donate old and unused musical instruments for area schoolchildren.

That is just the first action of a new initiative called Groundswell, an advocacy model that will offer people ways to not just consume culture, but actively use culture to improve the quality of life in Philadelphia.

"In our traditional advocacy model, we're working on advocacy in a pretty short time window, just around budget season -- when everyone's foaming at the mouth in Harrisburg or City Hall over who gets what. That's when, traditionally, we've been most active," said Michael Norris, an alliance vice president. "But, by having this broader approach, it allows us to be engaging people all the time."

The Arden Theater in Old City will formally launch Groundswell on Martin Luther King Jr. Day, with a free, public party at the end of the day of service.