The Music for the Inner City concert series in Anacostia continues with a concert at 5 p.m. Saturday at Barry Farms Recreational Park, Suitland Road and Firth Sterling Avenue SE. Three people from the audience will be selected to conduct a Sousa march featured in the program along with light classical works. Eight local musicians under the leadership of Darrold Hunt will perform. The series is sponsored by the Arts Connection and all concerts take place at different locations within a 15-block area in Anacostia. Call 699-5440 for further information . . .

The National Theatre invites artists to submit pencil sketch ideas for a poster to celebrate the theater's 150th Jubilee Year. The artist whose work is selected will receive $2,500, and the original art probably will be hung in the theater. Although there is no official deadline, the theater encourages artists to send their sketches in early. They will make their selection as soon as they have received enough entries. For more information call 783-3370 . . .

Guidelines and application materials for the D.C. Commission on the Arts and Humanities 1986 Constituencies Program grants are available. Grants under this program are awarded to District arts organizations and individual artists that support arts activities for groups outside the mainstream of the arts world -- the elderly, the institutionalized, the incarcerated and the mentally and physically handicapped.

About $50,000 will be awarded through the '86 program. Arts organizations may apply for up to $10,000 in project support; individuals may apply for up to $5,000. The application deadline is Sept. 27. Call 724-5613 for application materials and further information.