What kind of small social is it? How long is your rush process?
Socials are a great way to boost interest in joining. So maybe you just need to redefine your social. I know of chapters that have an 8 week recruitment process, and each week either kky or tbs have a rush social. The socials are almost always formatted the same way, with an activity or two (tie dye, improv, yard games, scavenger hunts) and food. The food is usually brought by chapter members or paid for in part by the chapter. And then the only rule is to have fun and don't say anything about kappa you wouldn't want said about you. It's a chance for the chapter members to show their true colors and act like fools.
Try putting together a brochure about Tau Beta Sigma. distribute it to the prospective freshman or whomever is your recruitment audience.
Other ideas include a rush service event. In the past, High School Band-Aid, cleaning out instruments and other similar music related service projects have been used for recruitment. Be creative.
You could also try a joint social with your Kappas showing that your chapters can work together.
Hope this helps. Let me know if you need anything else. You can e-mail me at
mwdvpm@tbs.org.