VOICES of Kentuckiana formed in 1994 to give gays, lesbians and supportive others the opportunity to sing together in a non-competitive environment. It's part of an international movement - LGBT choirs have flourished in metropolitan areas since the late 1970s, when the San Francisco Gay Men's Chorus paved the way for other chorale groups to help raise the visibility of LGBT and related social issues through musical performance. This weekend, the group celebrates its 20th anniversary with a reunion concert focused on the group's rich history and its legacy of advocacy.In addition to new musical theatre classics like RENT's "Seasons of Love" and WICKED's "For Good," the program includes three alumni numbers, when former members will join current singers on stage for "Hand In Hand," "Bridge Over Troubled Water" and "My Old Kentucky Home." The second half of the program will focus on the group's forward-thinking commitment to social justice and inclusion (VOICES is a non-audition choir), featuring "Imagine," "We Are Family" and "Just the Way You Are." The group performs twice this weekend (Friday, 7 p.m.; Sunday, 3 p.m.), with both shows at the Clifton Center's Eifler Theatre.