[aephi alum]

^ What HC said.

You might be able to get away with a blind recruitment for open houses during FR. No songs or chants that would give away the sorority. No mention of specific philanthropy activities that would identify the sorority - so a sister could say, "We volunteer at a soup kitchen once a month," but not "We went to the hospital to visit pediatric AIDS patients, because one of our philanthropies is the Elizabeth Glaser Pediatric - d'oh!". No letters, but maybe assign each chapter a random color (that might or might not be one of the sorority's colors) and have the sisters wear that color and mix it up from year to year - so, when the PNMs go to rank, they can list, say, red, yellow, green, and brown as their top choices and blue and purple as the chapters they'd rather not return to. Ask PNMs who can identify which chapter is which to keep mum, just like PNMs can be asked to keep mum if they know a particular recruitment counselor's affiliation.

Then, starting with the first invitation-only round, chapters reveal their identities. The chapters can then do activities related to their philanthropies for philanthropy round, do songs and skits that name the sorority, show off their houses if applicable, conduct their nationals-approved pref ceremonies, etc.

Social media adds a whole new layer of difficulty that didn't exist when I was a collegian (the World Wide Web was only just starting to take off). Chapters would have to pull all photos and rosters down from their web sites, and sisters (just like recruitment counselors) would have to scrub their social media presence to obscure their affiliation.

It might have worked 20 years ago. Today, it would be difficult to say the least.