The Baltimore Symphony Orchestra announced yesterday the offerings in the second season of a series targeted specifically at African-Americans. The five-concert series is called "Classically Black" and will include, in addition to four concerts by the BSO, a performance by the celebrated Harlem Boys Choir on Feb. 22 at Meyerhoff Hall.

The four other BSO concerts in the 1991-'92 series will feature pop singer Johnny Mathis (Oct. 3), pianist Andre Watts in Brahms Piano Concerto No. 2 (Oct. 17); soprano Harolyn Blackwell in Haydn's "The Creation" (Feb. 9); and the world-premiere performance of composer George Walker's "Folksongs for Orchestra" (May 22).

The concert series, which was inaugurated this season, was designed to increase the number of blacks in the BSO's audience by featuring African-American soloists and African-American composers. In yesterday's announcement, the orchestra called the 300 new subscribers attracted by this season's series "an overwhelming endorsement for the African-American presence."

Tickets for the five-concert series, priced at $85 and $105, may be purchased at the BSO box office or by calling 783-8000.