A "mixed" quartet is defined as having both male and female singers (although most mixed quartets are an even mix, two male/two female, not all are) which sings unacompanied 4-part harmony. It does not matter which part is sung by which person. Although it is desireable that member quartets include some "pure barbershop" songs in their current performing repertoire, it is not required.
It is expected, however, that ALL QUARTETS BE FAMILIAR WITH THE BARBERSHOP STYLE, and are able to identify the style of any song that they sing when they are in a "teaching mode." This is essential, since vaudeville and its barbershop quartet harmonies are the foundations of all of today's acappella quartet harmony styles.
While "mixed groups" (VLQ = very large quartet) are encouraged to become members, and the MHBQA currently has several VLQ members, the activities, information exchange, and newsletter is primarily directed to the 4-person quartet configuration. A mixed VLQ is defined as a group of more than four having both male and female singers, which sings unacompanied 4-part harmony without a director.
It should be noted that the Association also has "individual memberships," for persons or couples who are interested in the mixed barbershop area. See the "HOW DO I JOIN THE ASSOCIATION" for more information.